Etymology
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mainstream (n.)
also main-stream, main stream, "principal current of a river," 1660s, from main (adj.) + stream (n.); hence, "prevailing direction in opinion, popular taste, etc.," a figurative use first attested in Carlyle (1831). Mainstream media attested by 1980 in language of U.S. leftists critical of coverage of national affairs.
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pussy (n.2)

slang for "female pudenda," by 1879, but probably older; perhaps from Old Norse puss "pocket, pouch" (compare Low German puse "vulva"), or perhaps instead from the cat word (see pussy (n.1)) on the notion of "soft, warm, furry thing;" compare French le chat, which also has a double meaning, feline and genital. Earlier uses are difficult to distinguish from pussy (n.1), e.g.:

The word pussie is now used of a woman [Philip Stubbes, "The Anatomie of Abuses," 1583]

And songs such as "Puss in a Corner" (1690, attributed to D'Urfey) clearly play on the double sense of the word for ribald effect. But the absence of pussy in Grose and other early slang works argues against the vaginal sense being generally known before late 19c., as does its frequent use as a term of endearment in mainstream literature, as in:

"What do you think, pussy?" said her father to Eva. [Harriet Beecher Stowe, "Uncle Tom's Cabin," 1852]

Pussy-whipped "hen-pecked" is attested by 1956 (Middle English had cunt-beaten "impotent," in reference to a man, mid-15c.).

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