A verb for “traverse” in The Etymologies of the 1930s appearing in its Noldorin-style infinitive form trevedi derived from ON. tre-batie under the root ᴹ√BAT “tread” (Ety/BAT). Its stem form would thus be ✱trebat-, a combination of N. tre- “through” and N. ✱bad- “tread”.
Noldorin
tre-
prefix. through
tre-
prefix. through (but denoting completeness when prefixed to verbs, cf. English idioms like "talk something through")
trevad-
verb. to traverse
trî
preposition. through
A preposition meaning “through” in The Etymologies of the 1930s derived from ON. trī under the root ᴹ√TER(ES) “pierce” (Ety/TER), so presumably derived from ✱trē with ancient ē > ī as usual in Noldorin and Sindarin. In The Etymologies as published in The Lost Road Christopher Tolkien gave the Noldorin and Old Noldorin forms as trî and trí following the usual orthographic conventions of those languages (LR/392), but Carl Hostetter and Patrick Wynne indicated they were both trī in their Addenda and Corrigenda to the Etymologies (VT46/18).
godrebh
adverb. through together
tri
prefix. through (but denoting completeness when prefixed to verbs, cf. English idioms like "talk something through")
trî
preposition. through
A prefixal form of N. trî “through” in The Etymologies of the 1930s, appearing as tre- when unstressed (the norm) and tri- when stressed, though there are no examples of the latter (Ety/TER). Presumably this refers to ancient rather than modern stress.