can: [OE] English has two distinct words can. The verb ‘be able to’ goes back via Old English cunnan and Germanic *kunnan to an Indo- European base *gn-, which also produced know. The underlying etymological meaning of can is thus ‘know’ or more specifically ‘come to know’, which survived in English until comparatively recently (in Ben Jonson’s The Magnetick Lady 1632, for example, we find ‘She could the Bible in the holy tongue’).
This developed into ‘know how to do something’, from which we get the current ‘be able to do something’. The past tense could comes ultimately from prehistoric Germanic *kuntha, via Old English cūthe (related to English uncouth) and late Middle English coude; the l is a 16th-century intrusion, based on the model of should and would. (Canny [16] is probably a derivative of the verb can, mirroring a much earlier but parallel formation cunning.) Can ‘container’ appears to come from a prehistoric Germanic *kannōn-. => canny, cunning, ken, know, uncouth
Old English 1st & 3rd person singular present indicative of cunnan "know, have power to, be able," (also "to have carnal knowledge"), from Proto-Germanic *kunnan "to be mentally able, to have learned" (cognates: Old Norse kenna "to know, make known," Old Frisian kanna "to recognize, admit," German kennen "to know," Gothic kannjan "to make known"), from PIE root *gno- (see know).
Absorbing the third sense of "to know," that of "to know how to do something" (in addition to "to know as a fact" and "to be acquainted with" something or someone). An Old English preterite-present verb, its original past participle, couth, survived only in its negation (see uncouth), but see also could. The present participle has spun off as cunning.
Old English canne "a cup, container," from Proto-Germanic *kanna (cognates: Old Saxon, Old Norse, Swedish kanna, Middle Dutch kanne, Dutch kan, Old High German channa, German Kanne). Probably an early borrowing from Late Latin canna "container, vessel," from Latin canna "reed," also "reed pipe, small boat;" but the sense evolution is difficult.
Modern "air-tight vessel of tinned iron" is from 1867 (can-opener is from 1877). Slang meaning "toilet" is c. 1900, said to be a shortening of piss-can. Meaning "buttocks" is from c. 1910.
