The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
kwei-
DEFINITION:
Also kwye-. To rest, be quiet. Oldest forms *kwei1-, *kwye1-. Derivatives include while, coy, and requiem. I. Suffixed zero-grade form *kw-lo- (< *kwi-lo-). 1a.while, from Old English hwl, while; b.whilom, from Old English hwlum, sometimes. Both a and b from Germanic *hwl.2. Possibly Latin tranquillus, tranquil (trns, across, beyond; see ter-2): tranquil. II. Variant form *kwy- (< *kwye-). 1. Suffixed form *kwy-t-.requiem, from Latin quis, rest, quiet. 2. Suffixed form *kwy-ske-.coy, quiet, quit; acquiesce, acquit, quitclaim,quite, quitrent, requiescat, from Latin quiscere (past participle quitus), to rest. (Pokorny kei- 638.)