can (v.1)

Old English 1st & 3rd person singular present indicative of cunnan "to know," less commonly as an auxiliary, "to have power to, to be able," (also "to have carnal knowledge"), from Proto-Germanic *kunnjanan "to be mentally able, to have learned" (source also of Old Norse kenna "to become acquainted, try," Old Frisian kanna "to recognize, admit, know," German kennen "to know," Middle Dutch kennen "to know," Gothic kannjan "to make known"), from PIE root *gno- "to know."

It holds now only the third sense of "to know," that of "to know how to do something" (as opposed to "to know as a fact" and "to be acquainted with" something or someone). Also used in the sense of may, denoting mere permission. An Old English preterite-present verb, its original past participle, couth, survived only in negation (see uncouth), but compare could. The present participle has spun off with a deflected sense as cunning.

can (n.)

generally, "a small cylindrical sheet-metal vessel used to contain liquids, preserves, etc.," Old English canne "a cup, container," from Proto-Germanic *kanna (source also of Old Saxon, Old Norse, Swedish kanna "a can, tankard, mug," also a unit of measure, 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 sense of "air-tight vessel of tinned iron" is from 1867. Slang meaning "toilet" is c. 1900, said to be a shortening of piss-can; meaning "buttocks" is from c. 1910, perhaps extended from this.

can (v.2)

"to put up in cans," 1860, from can (n.1), especially "to put up in a sealed container for preservation." Sense of "to fire an employee" is from 1905. Related: Canned; canning.

updated on August 13, 2018

Definitions of can from WordNet
can (n.)
airtight sealed metal container for food or drink or paint etc.;
Synonyms: tin / tin can
can (n.)
the quantity contained in a can;
Synonyms: canful
can (n.)
a buoy with a round bottom and conical top;
Synonyms: can buoy
can (n.)
the fleshy part of the human body that you sit on;
Synonyms: buttocks / nates / arse / butt / backside / bum / buns / fundament / hindquarters / hind end / keister / posterior / prat / rear / rear end / rump / stern / seat / tail / tail end / tooshie / tush / bottom / behind / derriere / fanny / ass
can (n.)
a plumbing fixture for defecation and urination;
Synonyms: toilet / commode / crapper / pot / potty / stool / throne
can (n.)
a room or building equipped with one or more toilets;
Synonyms: toilet / lavatory / lav / john / privy / bathroom
can (v.)
preserve in a can or tin;
Synonyms: tin / put up
can (v.)
terminate the employment of; discharge from an office or position;
Synonyms: displace / fire / give notice / dismiss / give the axe / send away / sack / force out / give the sack / terminate
Etymologies are not definitions. From, not affiliated with etymonline.