vinegar n.

Old English win "wine," from Proto-Germanic *winam (source also of Old Saxon, Old Frisian, Old High German win, Old Norse vin, Dutch wijn, German Wein), an early borrowing from Latin vinum "wine," from PIE *uoin-a-, related to words for "wine" in other southern European languages (Greek oinos, Albanian Ghegvênë), also Armenian (gini), Hittite (uiian(a)-), and non-Indo-European Georgian and West Semitic (Arabic wain, Hebrew yayin).

According to Watkins, probably from a lost Mediterranean language word *win-/*woin- "wine." However, Beekes argues that the word is of Indo-European origin, related to Greek itea "willow," Latin vītis "vine," and other words, and they may be derived from the root *wei- "to turn, bend."

As the wild vine was indigenous in southern Russia and in certain parts of central Europe, this assumption is acceptable from a historical point of view. However, as the cultivation of the vine started in the Mediterranean region, in the Pontus area and in the south of the Caucasus, most scholars are inclined to look for the origin of the word in these countries. This would point to non-IE origin. However, if we put the homeland of viticulture in the Pontus and the northern Balkans, the word for 'wine' might come from there. [Beekes] 

Also from Latin vinum (some perhaps via Germanic) are Old Church Slavonic vino, Polish wino, Russian vino, Lithuanian vynas, Welsh gwin, Old Irish fin, Gaelic fion. Essentially the same word as vine (q.v.). Wine snob is recorded from 1951. Wine cellar is from late 14c. Wine-cooler is 1815 as "vessel in which bottled wine is kept cool;" by 1977 as a type of wine-based beverage.

late 13c., "strenuous, ardent, fierce, angry," from Old French aigre "sour, acid; harsh, bitter, rough; eager greedy; lively, active, forceful," from Vulgar Latin *acrus (source also of Italian agro, Spanish agrio), from Latin acer "keen, sharp, pointed, piercing; acute, ardent, zealous" (from PIE root *ak- "be sharp, rise (out) to a point, pierce").

Meaning "full of keen desire" (early 14c.) seems to be peculiar to English. The English word kept a secondary meaning of "pungent, sharp-edged" till 19c. (as in Shakespeare's "The bitter clamour of two eager tongues," in "Richard II"). Related: Eagerly; eagerness. Eager beaver "glutton for work" [OED] is from 1943, U.S. armed forces slang.