"girl, woman" (chaste or not, but especially one of roaming tendencies or loose morals), 1560s, canting jargon, and like most of it of unknown origin and no etymology.
"care, custody, charge," c. 1300, verbal noun from keep (v.). Phrase in keeping with "in harmony or agreement with" (1806) is from use of keeping in the jargon of painting to refer to a pleasing harmony of the elements of a picture (1715).
c. 1600, "provocative, exciting, encouraging," from Late Latin incentivus "inciting" (see incentive (n.)). In reference to a system of rewards meant to encourage harder work, first attested 1943 in jargon of the U.S. war economy.
1959, American English, originally teenager or beatnik slang, possibly a shortening of cuckoo.
Using the newest show-business jargon, Tammy [Grimes] admits, "I look kooky," meaning cuckoo. [Life magazine, Jan. 5, 1959]
Related: Kookily; kookiness.
early 13c., "a stroke, a blow," from kill (v.). Meaning "the act of killing" is from 1814 in hunting slang; that of "a killed animal" is from 1878. Lawn tennis serve sense is from 1903. The kill "the knockout" is boxing jargon, 1950. Kill ratio is from 1968, American English.