flip (v.) Look up flip at Dictionary.com
1590s (1520s in flip-flop), imitative or else a contraction of fillip (q.v.), which also is held to be imitative. Sense of "get excited" is first recorded 1950; flip one's lid "lose one's head, go wild" is from 1950. For flip (adj.) "glib," see flippant. Meaning "to flip a coin" (to decide something) is by 1879. As a noun by 1690s. Related: Flipped. Flipping (adj.) as euphemism for fucking is British slang first recorded 1911 in D.H. Lawrence. Flip side (of a gramophone record) is by 1949.
flip (n.) Look up flip at Dictionary.com
sailors' hot drink usually containing beer, brandy and sugar, 1690s, from flip (v.); so called from notion of it being "whipped up" or beaten.