1823, "the fitting of one thing to another," later (1831) "the way something fits." Originally "an adversary of equal power" (mid-13c.), obscure, possibly from Old English fitt "a conflict, a struggle" (see fit (n.2)).
"paroxysm, sudden attack" (as of anger), 1540s, probably via Middle English sense of "painful, exciting experience" (early 14c.), from Old English fitt "conflict, struggle," of uncertain origin, with no clear cognates outside English. Perhaps ultimately cognate with fit (n.1) on notion of "to meet." Phrase by fits and starts first attested 1610s.
part of a poem, Old English fitt, of unknown origin.
"suited to the circumstances, proper," mid-15c., of unknown origin, perhaps from Middle English noun fit "an adversary of equal power" (mid-13c.), which is perhaps connected to fit (n.1). Related: Fitter; fittest. Survival of the fittest (1867) coined by H. Spencer.
"be suitable," probably from early 15c.; "to be the right shape," 1580s, from fit (adj.). Related: Fitted; fitting. Fitted sheets is attested from 1963.
fit 1 (fĭt)
v. fit·ted or fit, fit·ted, fit·ting, fits
To be the proper size and shape. adj. fit·ter, fit·test
Physically sound; healthy. n.
The degree of precision with which surfaces are adjusted or adapted to each other in a machine, device, or collection of parts.
fit 2 (fĭt)
A seizure or a convulsion, especially one caused by epilepsy.
The sudden appearance of a symptom such as coughing or sneezing.
To behave or react very angrily; have kittens: She just about threw a fit when I told her we weren't going/ Well, they threw a spaz and said I can't see him or have him over (entry form 1896+, variant 1990s+)