Old English ham, hom (originally denoting the back of the knee), from a Germanic base meaning 'be crooked'. In the late 15th cent. the term came to denote the back of the thigh, hence the thigh or hock of an animallate 19th cent. (originally US): perhaps from the first syllable of amateur; compare with the US slang term hamfatter 'inexpert performer'. Sense 2 dates from the early 20th cent
