Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
jamb, jam (nn.)
Of these homophones, jamb means “the side frame member of a door or other opening”: The lefthand door jamb was splintered. Jam (1) is a functional shift from the verb jam, meaning “to squeeze or wedge or crowd together”; the noun means “a crowd or mass of people or things,” as in There was a large log jam in the river; A traffic jam blocked the intersection. This word also has a Conversational and Informal sense meaning “a difficulty, a predicament,” as in Having lost my billfold, I was in a real jam. Jam (2) is the confection made by boiling fruit to use as a spread for toast. All except the “predicament” sense are fully Standard.
