c. 1400, "backbone," later "thornlike part" (early 15c.), from Old French espine "thorn, prickle; backbone, spine" (12c., Modern French épine), from Latin spina "backbone," originally "thorn, prickle" (figuratively, in plural, "difficulties, perplexities"), from PIE *spe-ina-, from root *spei- "sharp point" (see spike (n.1)). Meaning "the back of a book" is first attested 1922.
late 14c., intransitive, "to feel cold, grow cold;" c. 1400, transitive, "to make cold," from chill (n.). Related: Chilled; chilling; chillingly. Figurative use "discourage, dispirit" is from late 14c. Meaning "hang out" first recorded 1985; from earlier chill out "relax" (1979).
Sheila E. sizzles in the new flick, Krush Groove, but some New York critics couldn't groove with it because many of the terms are unfamiliar to them. Examples: breakin' out (slang for leaving), chill (for cool down) and death (for something that's really good). [Jet, Nov. 11, 1985]