1670s, "offensive to a refined sense of propriety, beyond the bounds of proper reserve," from in- (1) "not, opposite of" + delicate. Related: Indelicately.

Immorality and indelicacy are different things. Rabelais is indelicate to the last degree, but he is not really immoral. Congreve is far less indelicate, but far more immoral. [James Hadley, "Essays Philological and Critical," 1873]

also nonny-nonny, 1530s, an unmeaning refrain word in older English ballads, similar to the fa la of madrigals, often used "as a cover for indelicate allusions" [Century Dictionary].

"to expurgate by eliminating indelicate or offensive passages," 1836, from Thomas Bowdler, English editor who in 1818 published a notorious expurgated Shakespeare, in which, according to his frontispiece, "nothing is added to the original text; but those words and expressions omitted which cannot with propriety be read aloud in a family." Related: Bowdlerized; bowdlerizing; bowdlerization.