In Middle English, "any source of pleasure or delight," also "an appetite," also "a liking for a person," also "fertility" (of soil). Specific and pejorative sense of "sinful sexual desire, degrading animal passion" (now the main meaning) developed in late Old English from the word's use in Bible translations (such as lusts of the flesh to render Latin concupiscentia carnis in I John ii:16); the cognate words in other Germanic languages tend to mean simply "pleasure." Masculine in Old English, feminine in modern German.
"amorous or designing widow," 1907, from the English title of Franz Lehar's operetta "Die Lustige Witwe" (1905). "The Lusty Widow" would have been more etymological (see lust (n.)), but would have given the wrong impression in English. Meaning "a type of wide-brimmed hat" (popularized in the play) is attested from 1908.