Meaning

noun preserve of crushed fruit

noun informal terms for a difficult situation

noun a dense crowd of people

originFirst attested in the early 18th c. as a verb meaning “to press, be pressed, be wedged in”. Compare dialectal jammock (“to press, squeeze, crush into a soft mass, chew food"; also "a soft, pulpy substance”). Perhaps from Middle English chammen, champen ("to bite upon something, gnash the teeth"; whence modern champ, chomp), of uncertain origin; probably originally onomatopoeic. The "performance"…

Etymology from Wiktionary, CC BY-SA 3.0