subtle

The adjective is derived from Middle English sotil, soubtil, subtil (“of a person, the mind, etc.: clever, ingenious, penetrating; cunning, sly; insidious; delicate, fine; not dense, light, thin; finely powdered; narrow, slender; etc.”), borrowed from Anglo-Norman sotel, subtil, sutil, Middle French soutil, subtil, sutil, and Old French sotil, soutil, subtil, sutil (“of an object: skilfully designed or made; delicate, fine; slender, thin; of an intangible thing: difficult to understand; of a person: discerning, shrewd; devious, sly; etc.”) (modern French subtil), from Latin subtīlis (“of texture: delicate, fine; slender, thin; accurate, keen; having fine judgment; etc.”), from sub (“below, under”) + tēla (“warp (threads running lengthwise in a loom); web”) (ultimately from Proto-Indo-European *tetḱ- (“to create, produce; to cut, hew”), from *teḱ- (“to beget, sire”)). The word displaced Old English smēag (literally “creeping”).

The modern and Middle English (and French) spellings with -b- are influenced by Latin subtīlis; the letter was probably never pronounced.

The noun is derived from Middle English sotil, soubtil, subtil (“wise person; sophisticated people collectively”), from the adjective.