beach- c.1535, probably from O.E. bæce, bece "stream," from P.Gmc. *bakiz. The initial extension was to loose, pebbly shores (1596), and in dialect around Sussex and Kent beach still has the meaning "pebbles worn by the waves." Fr. grève shows the same evolution. The verb "to haul or run up on a beach" is first attested 1840. Beach bum first recorded 1962. Beachhead (1940) is on the model of bridgehead.

guy- 1847, originally Amer.Eng.; earlier (1836) "grotesquely or poorly dressed person," originally (1806) "effigy of Guy Fawkes," leader of the Gunpowder Plot to blow up British king and Parliament (Nov. 5, 1605), paraded through the streets by children on the anniversary of the conspiracy. The male proper name is from Fr., related to It. Guido, lit. "leader," of Gmc. origin

in- Sense of "holding power" (the in party) first recorded 1605; that of "exclusive" (the in-crowd, an in-joke) is from 1907; that of "stylish, fashionable" (the in thing) is from 1960. The noun sense of "influence, access" (have an in with) first recorded 1929 in Amer.Eng. The suffix -in attached to a verb originated 1960 with sit-in, probably infl. by sit-down strike, used first of protests, extended c.1965 to any gathering. In-and-out "copulation" is attested from 1620. To be in like Flynn is 1940s slang, said to be U.S. military, perhaps from alleged sexual exploits of Hollywood actor Errol Flynn.

thongs- O.E. þwong "thong, narrow strip of leather (used as a cord, band, strip, etc.)," from P.Gmc. *thwangaz (cf. O.N. þvengr), from PIE base *twengh- "to press in on, to restrain." As a kind of sandal, first attested 1965; as a kind of bikini briefs, 1990.