Meaning

adjective (usually followed by `to') naturally disposed toward

adjective at risk of or subject to experiencing something usually unpleasant

adjective mentally quick and resourceful; ; -Bram Stoker

originFrom Old French apte, from Latin aptus (“suitable, fitting”). Either from obsolete apere (“to fasten, to join, to fit”), akin to apisci (“to reach, attain”) (compare with Greek ἅπτειν (áptein, “to fasten”) and Sanskrit आप्त (āpta, “fit”), from आप् (āp, “to reach, attain”)) or from *h₂ep- (“to join, fit (in)”).

Etymology from Wiktionary, CC BY-SA 3.0