mid-13c., "to end at, to border on, touch at the end," from Old French aboter, abuter "join end to end, touch with an end" (13c.), and abouter "join end to end," from à "to" (see ad-) + boter, bouter "to strike, push," from a Germanic source (ultimately from PIE root *bhau- "to strike"). Compare butt (v.). Related: Abutted; abutting.
late 14c. in Latin form abyssus, "depths of the earth or sea; primordial chaos;" early 14c. as abime "depths of the earth or sea; bottomless pit, Hell" (via Old French; see abysm). Both are from Late Latin abyssus "bottomless pit," from Greek abyssos (limnē) "bottomless (pool)," from abyssos "bottomless, unfathomed," hence, generally, "enormous, unfathomable," also as a noun, he abyssos "the great depth, the underworld, the bottomless pit." This is a compound of a- "without" (see a- (3)) + byssos "bottom," a word of uncertain origin possibly related to bathos "depth" [Liddell & Scott]. Watkins suggests a connection with the root of bottom (n.); Beekes suggests it is pre-Greek.
The current form in English is a 16c. partial re-Latinization. Greek abyssos was used in Septuagint to translate Hebrew tehom "original chaos" and was used in the New Testament for "Hell." OED notes, "the word has had five variants, abime, abysm, abysmus, abyssus, abyss; of which abyss remains as the ordinary form, and abysm as archaic or poetic." In reference to a seemingly bottomless gulf from 1630s. Old English glossed Latin abyssum with deagenesse, which is related to deagol "secret, hidden; dark, obscure."
1540s, type of shrub or tree fund in warm climates of Africa and Australia, from Latin acacia, from Greek akakia "thorny Egyptian tree," a word of uncertain origin. Perhaps it is related to Greek akē "point, thorn" (from PIE root *ak- "be sharp, rise (out) to a point, pierce"), or perhaps it is a Hellenization of some Egyptian word. Beekes suggests it is probably a word from a pre-Greek Mediterranean language and finds "no reason for an Oriental origin." Greek kaktos also has been compared. From late 14c. in English as the name of a type of gum used as an astringent, etc. Extended 17c. to North American trees.