c. 1300, sotil; modern form from late 14c., "clever, dexterous, crafty; not dense, thin, rarefied," from Old French subtil (14c.), a learned Latinized reformation of earlier sotil (12c.), source of subtle (q.v.). Still used in some Bible translations in Genesis iii.1, and it survived after 17c. as a parallel formation to subtle in some material senses ("fine, delicate, thin"). Related: Subtilly.