First, let me make a small digression and compare tram to drum (Ger. Trommel) and to Greek δρόμος (course, race-course, lap, public walk, road, track, way)… and to Serbian drum (road) in addition. Vasmer mentions the Russian words udaritь, derú, dratь, razdor (from O.Slav. oudariti “slam, strike, hit, ram”; Serb. udariti, udar, udaram “blow, stroke, strike, beat, kick, knock, push”; s-udar-anje “clash, shock, collision, crash, impact, smash”) and compares it to Greek δῆρις, -ἡ “battle, contest”. Here it seems also to be interesting to mention that Old Slavic derѫ, dьrati (d”rati “tear, flay”) is a cognate to Sanskrit dr̥ṇā́ti (tear, split) and Greek δέρω (separate by avulsion, skin, flay; hence the Greek noun δέρμα “skin, hide”). All these words are derived from the same proto-form similar to *xər-bhl-gən.; i.e. from its contracted basis – *xər-gon.
English track is probably the source of Serbian traka (band, ribbon) and it is farther (reversibly) related to Serbian trag (trace, footprint, mark, track) as well as to the Russian word doroga (road, path). One of the first thing we must have in mind here is that the most of those *thər- words are derived from an earlier agglutinated form, which sounded similar to *thuer-bəl-gon (Eng. turbid, turbulence, turbine, curving, trouble, Gr. τύρβη “tumult, disorder”, Lat. turbidus; cf. Serb. turoban “mirky, gloomy”). In this case, the semantic shifts are remarkable: for instance, German trommeln (drum, beat out, pound, batter) is the word from the same “arsenal” as Serbian grmljavina (thunder, thundering; hence Serb. grom “thunder”; OSlav. gromъ; Gr. χρόμᾰδος “crashing sound”, τρίβω “to rub, thresh”; τριβόμενος “frictional”; Serb. trljanje, trenje “friction”, Russ. trenie “friction”; Cz. tření).
Another word, that should be thoroughly examened, is English group (Ita. gruppo). This word has been developed following the same logic as the above-mentioned “turbulence”. As a matter of fact, turbulence must be a “descendent” word in comparison to group, because the grouping is a precondition for a certain kind of “turbulant activities” in the future. Group is closely related to grab (Ger. graben “dig, grub, burrow”, Serb. grabiti “catch, grab”, OSlav. grabiti, Serb. grablje “rake”) and grave (Ger. Grab, Serb. grob; OSlav. grobъ).
Serbian krupno (big) and ukrupnjenje (making bigger) are the close relatives to Serbian ogroman (large, big, enormous, giant, huge), and all of these words are derived from the above-mentioned ur-basis — *xər-bhl-gən.
The protoform *xər-bhl-gən is in fact a “twofold or doubled roundness”. It entails that the primary meaning of such agglutinated word was ring + ball : Gr. κρίκος “ring” + ἀμφέλκω “be surrounded by”; Serb. krug “circle” + oblo “round”; Ger. Ring + Ball, like in kurbeln “wind”, Kurbel “winder”; Lat. circus + oval or bulla “round swelling”, OE hring “circle” + bolla “round object, cup, bowl”; cf. OE hring-boga “snake” and Icel. hring-laginn “coiled up”, both from hypothetical *hring-bləg(n), i.e. in sense “bent in circle” or “coiled being” (hence probably the Serbian n. rugoba “a monstrous creature” and adj. rugoban “monstrous, ugly”). Greek Charybdis (Χάρυβδις) is a word equal to Serbian grdoba “monstrous creature”, while Serbian grdoba is just a variant of the above-mentioned rugoba (from *h/rugoba => *gruhoba => grdoba). The name crocodile appears to be obtained in a similar way —*hro(ho)b(d)ile; (cf. Ir. crogall, Sc. eireallach “a monster”, eirbleach “slack-jointed or crippled person, Sc. hirplock “lame creature, cripple”, OSl. hromъ, Serb. hrom, hramati “lame, to limp”, Skt. स्राम srāmá “lame”, Eng. horrible “horrifying, ugly”). Alslo there is Gaelic rìbhinn “maid, nymph, serpent, beautifull female”, which might be related to Old Slavic rыba “fish” (Serb. riba; cf. Lat. rubeta “toad”) and German Raupe “caterpillar”.
We can see that Gaelic cruimhean “worms” sounds close to rìbhinn and cruimh “worm”, and Latin vermis (worm) must be obtained from the same language “depot” of “curved creatures” (Ger. gekrümmt, krumm “bent, curved, curled”; Lith. kirminas, kirmėlė “worm”; Skt. कृमिन् kṛmin “worm”) as it happened to PSl. *čьrvь (OSl. črьvь “worm”, Russ. červь, Serb. crv). In fact, in this case, the “curved line” is a basic “motto” in depicting some unusual or even unnatural characteristic (Serb. kriv-ljenje “bending, distortion”, Russ. krivoй “distorted”, is-kriv-lenie “distortion, deformation, curvature”).
In order to understand how the initial *kərb- “root” (from proto-form *xər-bhl-gən) changed its appearance and became *kərp-, *kərv-, *kərm-or *kərf let us compare Latin crimen “a judgment, charge, accusation, reproach” (Gr. κρι̂μα “a decision, judgment”) with the South-Slavic krivica (guilt, culpability; krivina “curve”; OSl. krivъ “crooked”, Serb. kriv “crooked, incorrect, guilty”; Cz. křivý”crooked, awry, incorrect, improper, deceitful”; Gr. κροιός “having deformity”; Lith. kreivas “crooked, curved, wry, wrong, false, unfair”). The crucial question here is whether the Latin word crimen is or not related to Serbian krivnja “culpability”.
Of course, worm (Serb. crv “worm”) is not guilty (Serb. kriv “guilty”) for his curly or curved (Serb. kriv “curved, crooked, bent”) appearance. Similar can be spoken about the relation among Slavic crevo (OSl. črѣvo, Serbian crevo; Cz. střevo), which has two meanings: intestine and hosepipe. In both cases, we have to deal with the curved/hollowed – cablelike objects. The same “curved” logic is well visible among the Greek words κοιλία “cavity of the body, belly, abdomen, intestines”, κοῖλος “hollow, concave, cavernous” and σκολιός “curved, winding, twisted, tangled” (cf. Slav. kolo “wheel, circle”; OSl. kolo). Even the word for worm followed the same pattern as it was seen above (Gr. σκώληξ “worm”; literary, a twisted, curved creature) in Slavic and Germanic languages.
In Old Prussian, intestine was named grābs, phonetically very close to German Grab “grave” and Slavic grab (hornbeam; genus Carpinus). Is there anything at all that would be able to connect those three words? On the other hand, OPr. kērmens “body” (Latv. ķermenis “body”) appears to be related to Ger. Körper and Lat. corpus, while OPr. kīrms “worm” (Latv. cērme “worm”) seems to be related to “body” (corpus) in a certain, maybe unusual way?
Latin trabs “a beam of wood, tree-trunk” is a possible cognate to the Serbian word trup “body, trunk, torso, corpus” (OSl. troupъ, Cz. trup; Russ. trup) and there is another Serbian word (trupac “beam of wood, tree-trunk”) – whose meaning is exactly the same as the meaning of Latin trabs.
One thing is very interesting here. Namely, the English words tramp, trample (MLG trampen “walk heavily, stamp”) and stamp (OE stempan “stamp”) are the cognates of the Serbian verbs trapati “walk heavily” (n. trapanje; adj. trapav “awkward, clumsy”) and stupati “march” (n. stupanje “marching”). Both of these Serbian words are related to the tree stem (Serb. stablo “stem, bole, trunk”; Russ. stebelь, stvol; Cz. stéblo) or tree-trunk (Serb. trupac, truplo “tree-trunk”). Not casually, Serbian stablo “stem, stalk” is used in naming of the most distal part of human leg — stopalo “foot” (OSl. stopa; Russ. stupnя, stopa; Cz. stopa), because of the similarity between tree stem and human leg. The almost same relation could be seen in Germanic: Eng. stem (from *stebh-l-; Ger. Stiel, Stamm, Stengel ), step, Ger. Stufe “step, stair, grade, degree; cf. Serb. stepen, stupanj “grade, degree”, stepenice “steps, stairs”.
Latin ramus “bough, branch, twig” looks as if it has nothing to do with Serbian grana “branch”. Nevertheless, both words are probably derived from the same “root” (*grəbh-gn-), which is, in fact, one of the variations of the primeval form *xər-bhl-gən (“a curved line”). Perhaps this would be clearer if we compared Latin ramale -is “brushwood” with the Serbian grmlje “brushwood”. The Greek word for thicket is δρυμός; as we can see, phonetically very close to δρόμος (a public walk, colonnade, from δραμει̂ν , aor. inf. of τρέχω “to run”). Now it becomes possible that Lat. ramus is a cognate to above-mentioned trabs “beam of wood”. In Russian, the noun hrebet “ridge, edge, spine” (Serb. hrbat “back”, greben “ridge”) is the antecedent of granь “verge, edge, margin, boundary” (Serb. granica “boundary, border”, grana “twig, branch, limb”).
Semantic shifts in these cases seem to be unexpected, but if we supposed that thousands and thousands of words were sprang from the same source, then such shifts should not be seen as startling. For instance, Serbian grumen “lump of soil, clod, clump, turf” (Russ. grum) is probably the same word as Latin gramen “grass, turf, herb” and these two words may be distantly related to Serbian trava “grass” (OSl. trava, Pol. trawa) and Latin herba “herb, grass”. In this context, the Slavic appelative d(e)revo (OSl. drѣvo; Russ. derevo; Pol. drzewo) might be from the same origin as trava “grass”. As it is quite obvious, now we are entering the field of pure guessing.
Maybe it would be interesting to mention the Czech words křoví, křoviny “bush, shrub, scrub”, travina “grass” and dřevo “wood, timber”, i.e. dřevina “woody species”. Czech křoví “bush” is probably a false friend to Serbian korov “weed” (cf. Serb. adj. za-korovljeno = za-travljeno “weedy”; Russian sornaя trava “drossy grass, weed”). The OE syntagm grēne græs might be an indication that green is related to grass. Swedish gren has the same mening as Serbian grana (branch; Dan. grene sig “branch out”), and both of these words must be derived from the same proto-word (*grebhn-; Serb. greben, hrbat, hrid “ridge, cliff”). The OE compound word hrycg-weg “an elevated piece of ground, ridge-way” (Serb. greben “ridge”, hrid-ina “cliff”) is composed of two words: hrycg (from hring “ring”) and weg “road, way”(from IE *bhelg-; Russ. bežatь, ubegatь “run”, Cz. běh, běžet “run”; Latin pello, pellere, pepuli, pulsus “drive out”, veho, vehere “carry, ride, sail”; also Serb. beg, bežati “running away”, voziti “drive”; cf. Serb. vozilo – from *vogi-kolo “drive the wheel” or *begi-kolo “the running wheel, cart, wagon” – and Lat. vehiculum, vehi-culi).