1869, "having the color of raw silk or unbleached linen," from French écru "raw, unbleached," from Old French escru "raw, crude, rough" (13c.), from es- "thoroughly" (see ex-) + Latin crudus "raw" (see crude).
word-forming element, in English meaning usually "out of, from," but also "upwards, completely, deprive of, without," and "former;" from Latin ex "out of, from within; from which time, since; according to; in regard to," from PIE *eghs "out" (source also of Gaulish ex-, Old Irish ess-, Old Church Slavonic izu, Russian iz). In some cases also from Greek cognate ex, ek. PIE *eghs had comparative form *eks-tero and superlative *eks-t(e)r-emo-. Often reduced to e- before -b-, -d-, -g-, consonantal -i-, -l-, -m-, -n-, -v- (as in elude, emerge, evaporate, etc.).
late 14c., "in a raw or unprepared state" (of coarse bread or untanned hide), from Latin crudus "rough; not cooked, raw, bloody," from PIE *krue-do-, from PIE root *kreue- "raw flesh." Meaning "lacking grace, socially unrefined" is attested by 1640s. Related: Crudely; crudeness. Crude oil, which is in its natural state and unrefined, is from 1865.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit kravis- "raw flesh," krura- "raw, bloody;" Greek kreas "flesh;" Latin crudus "bloody, raw; cruel," cruor "thick blood;" Old Irish cru "gore, blood," Middle Irish cruaid "hardy, harsh, stern;" Old Church Slavonic kry "blood;" Old Prussian krawian, Lithuanian kraūjas "blood;" Old English hreaw "raw," hrot "thick fluid, serum."
<a href="https://www.etymonline.com/word/ecru">Etymology of ecru by etymonline</a>
Harper, D. (n.d.). Etymology of ecru. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/ecru