Subtle
Middle English (also in the sense ‘not easily understood’): from Old French sotil, from Latin subtilis .
wiktionary
From Middle English sotil, soubtil, subtil, borrowed from Old French soutil, subtil, from Latin subtīlis(“fine, thin, slender, delicate”); probably, originally, “woven fine”, and from sub(“under”) + tela(“a web”), from texere(“to weave”). Displaced native Old English smēag.
etymonline
subtle (adj.)
c. 1300 (mid-13c. as a surname), sotil, "penetrating; ingenious; refined" (of the mind); "sophisticated, intricate, abstruse" (of arguments), from Old French sotil, soutil, subtil "adept, adroit; cunning, wise; detailed; well-crafted" (12c., Modern French subtil), from Latin subtilis "fine, thin, delicate, finely woven;" figuratively "precise, exact, accurate," in taste or judgment, "fine, keen," of style, "plain, simple, direct," from sub "under" (see sub-) + -tilis, from tela "web, net, warp of a fabric," from PIE root *teks- "to weave," also "to fabricate." According to Watkins, the notion is of the "thread passing under the warp" as the finest thread.
From early 14c. in reference to things, "of thin consistency;" in reference to craftsmen, "cunning, skilled, clever;" Depreciative sense "insidious, treacherously cunning; deceitful" is from mid-14c. Material senses of "not dense or viscous, light; pure; delicate, thin, slender; fine, consisting of small particles" are from late 14c. sotil wares were goods sold in powdered form or finely ground. Partially re-Latinized in spelling, and also by confusion with subtile.
