drinkable adj.

Old English drincan "to swallow water or other fluid," also "to swallow up, engulf" (class III strong verb; past tense dranc, past participle druncen), from Proto-Germanic *drenkanan (source also of Old Saxon drinkan, Old Frisian drinka, Dutch drinken, Old High German trinkan, German trinken, Old Norse drekka, Gothic drigkan "to drink"), which is of uncertain origin or connections, perhaps from a root meaning "to draw."

Most Indo-European words for this trace to PIE *po(i)- (source of Greek pino, Latin biber, Irish ibim, Old Church Slavonic piti, Russian pit'; see imbibe).

Figurative meaning "take in through the senses" is from late 12c. Especially "to imbibe spiritous liquors" from mid-15c. To drink to "salute in drinking" is by mid-13c. To drink like a fish is recorded from 1744. To drink (someone) under the table "continue drinking and remain (comparatively) sober after others have passed out" is by 1909.

common termination and word-forming element of English adjectives (typically based on verbs) and generally adding a notion of "capable of; allowed; worthy of; requiring; to be ______ed," sometimes "full of, causing," from French -able and directly from Latin -abilis. It is properly -ble, from Latin -bilis (the vowel being generally from the stem ending of the verb being suffixed), and it represents PIE *-tro-, a suffix used to form nouns of instrument, cognate with the second syllables of English rudder and saddle (n.).

A living element in English, used in new formations from either Latin or native words (readable, bearable) and also with nouns (objectionable, peaceable). Sometimes with an active signification (suitable, capable), sometimes of neutral signification (durable, conformable). It has become very elastic in meaning, as in a reliable witness, a playable foul ball, perishable goods. A 17c. writer has cadaverable "mortal."

To take a single example in detail, no-one but a competent philologist can tell whether reasonable comes from the verb or the noun reason, nor whether its original sense was that can be reasoned out, or that can reason, or that can be reasoned with, or that has reason, or that listens to reason, or that is consistent with reason; the ordinary man knows only that it can now mean any of these, & justifiably bases on these & similar facts a generous view of the termination's capabilities; credible meaning for him worthy of credence, why should not reliable & dependable mean worthy of reliance & dependence? [Fowler]

In Latin, -abilis and -ibilis depended on the inflectional vowel of the verb. Hence the variant form -ible in Old French, Spanish, English. In English, -able tends to be used with native (and other non-Latin) words, -ible with words of obvious Latin origin (but there are exceptions). The Latin suffix is not etymologically connected with able, but it long has been popularly associated with it, and this probably has contributed to its vigor as a living suffix.