subtile
/ˈsʌtl/ /ˈsʌbt(ɪ)l/(also subtil) Now rare (chiefly superseded by subtle)
adjective
Of the nature of or involving careful discrimination or fine points.
Origin
Late Middle English (in an earlier sense). Probably partly (i) from Anglo-Norman and Middle French subtil, soubtil, variants of sutil, soutil.