1808 (in acetic acid), from French acétique "pertaining to vinegar, sour, having the properties of vinegar," from Latin acetum "vinegar" (properly vinum acetum "wine turned sour;" see vinegar), originally the past participle of acere "be sharp; be sour" (related to acer "sharp," from PIE root *ak- "be sharp, rise (out) to a point, pierce").
"to heap up," 1610s, from Latin acervatus, past participle of acervare "to heap up," from acervus "heap," which is akin to acer "sharp" (from PIE root *ak- "be sharp, rise (out) to a point"). Related: Acervated; acervating; acerval; acervative; acervuline "occurring in clusters; clustered" (by 1859).
1865, originally, and usually, figurative: "sour, harsh, severe" (of speech, manners, etc.), from Latin acerbus "harsh to the taste, sharp, bitter, sour," especially of unripe fruits, etc., also figuratively, of character, conduct, etc. (see acerbity) + -ic. The earlier adjective was simply acerb (1650s), from French acerbe, from Latin acerbus.
"sourness, with roughness or astringency of taste," 1570s, from French acerbité, from Latin acerbitatem (nominative acerbitas) "harshness, sharpness, bitterness, sourness," literal and figurative (as in virus acerbitatis "the poison of malice"), from acerbus "bitter to taste, sharp, sour, tart," from Proto-Italic *akro-po- "sharp" (from PIE root *ak- "be sharp, rise (out) to a point, pierce"). The earliest use in English is figurative, of "sharp and bitter" persons. Of tastes, from 1610s. Latin acerbus is related to acer "sharp" as superbus "haughty" to super "above."
maple tree genus name, from Latin acer, a word of uncertain origin, perhaps from PIE *ak- "be sharp" (see acro-) and so called for its pointed leaves. There seem to have been two roots for "maple" in Indo-European; cognates of this one are said to include Old High German ahorn "maple," and there is a similar form in Greek akastos "maple," perhaps also Hittite hiqqar- "maple." De Vaan writes, "This may well be a non-PIE tree name which was borrowed into Greek and Latin."