"good faith, fair dealing, freedom from intent to deceive," by 1838, English pluralization of bona fide, as though the Latin phrase were a noun. Sense of "guarantees of good faith" is by 1944. The opposite is mala fides "bad faith, intent to deceive."
also hoochie-coochie, hootchy kootchy, "erotic suggestive women's dance" (involving a lot of hip-grinding), 1898, of obscure origin, usually associated, without evidence, with the Chicago world's fair of 1893 and belly-dancer Little Egypt (who might not even have been there), but the word itself is attested from 1890, as the stage name of minstrel singer "Hoochy-Coochy Rice," and the chorus of the popular minstrel song "The Ham-Fat Man" (by 1856; see ham (n.2)) contains the nonsense phrase "Hoochee, kouchee, kouchee."
To-day, however, in place of the danse du ventre or the coochie-coochie we have the loop-the-loop or the razzle-dazzle, which latter, while not exactly edifying at least do not serve to deprave public taste. ["The Redemption of 'Old Coney,'" in Broadway Magazine, April 1904]
1520s, the earliest recorded sense is "mistress;" the allusion to grass is not clear, but it commonly was believed to refer to casual bedding (compare bastard and German Strohwitwe, literally "straw-widow," and compare the expression give (a woman) a grass gown "roll her playfully on the grass" (1580s), also euphemistic for the loss of virginity). Revived late 18c. as "one that pretends to have been married, but never was, yet has children;" in early 19c. use it could mean "married woman whose husband is absent" (and often presumed, but not certainly known to be, dead), also often applied to a divorced or discarded wife or an unmarried woman who has had a child. Both euphemistic and suggestive.
[G]rasse wydowes ... be yet as seuerall as a barbours chayre and neuer take but one at onys. [More, 1528]
GRASS WIDOW, s. a forsaken fair one, whose nuptials, not celebrated in a church, were consummated, in all pastoral simplicity, on the green turf. [Rev. Robert Forby, "Vocabulary of East Anglia," London, 1830]