Other Indo-European languages often have separate words for "tin" as a raw metal and "tin plate;" such as French étain, fer-blanc. Pliny refers to tin as plumbum album "white lead," and for centuries it was regarded as a form of silver debased by lead; hence its figurative use for "mean, petty, worthless." The chemical symbol Sn is from Late Latin stannum (see stannic).
Meaning "container made of tin" is from 1795. Tin-can is from 1770; as naval slang for "destroyer," by 1937. Tin-type in photography is from 1864. Tin ear "lack of musical discernment" is from 1909. Tin Lizzie "early Ford, especially a Model T," first recorded 1915.
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.
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.