sweat (v.)

Middle English sweten, from Old English swætan "perspire, excrete moisture from the skin," also "toil, labor, work hard," from Proto-Germanic *swaitjan "to sweat," from the source of sweat (n.). Compare Frisian swette, Dutch zweeten, Danish svede, German schwitzen.

The meaning "be worried, vexed" is recorded from c. 1400. The transitive sense of "cause to excrete moisture" is from late 14c. Related: Sweated; sweating.

Middle English swete, alteration of swot, swoet, from Old English swat "perspiration, moisture exuded from the skin in drops through the pores," also "labor, that which causes sweating" (also sometimes "blood"), from Proto-Germanic *swaitaz "sweat" (source also of Old Saxon, Old Frisian swet, Old Norse sveiti, Danish sved "sweat," Swedish svett, Middle Dutch sweet, Dutch zweet, Old High German sweiz, German Schweiß).

In Pokorny and Watkins this is from PIE *sweid- "to sweat," source also of Sanskrit svedah "sweat," Avestan xvaeda- "sweat," Greek hidros "sweat, perspiration," Latin sudor, Lettish swiedri, Welsh chwys "sweat." A widespread set of Slavic words (Polish, Russian pot "sweat") is from Old Church Slavonic potu, which is related to peku "heat," a word cognate with Latin coquere.

The Old English noun became Middle English swote, but took its current form under the influence of the verb. Extended to any exuded drops of moisture by late 14c. The meaning "condition of sweating, state of one who sweats or perspires" as a result of exertion, heat, etc. is by c. 1400, hence "short run of a horse for exercise" (c. 1700).

Sweat of (one's) brow as a symbol of toil (late 14c.) is from Genesis iii.19. Sweat equity is attested from 1968, in reference to the interest in property accrued by those who have maintained or improved it but do not own it (originally of squatters in municipal tenements). Sweat-labor (1670s) was used of the works and sufferings of the martyrs and Apostles.