Apt
late Middle English (in the sense ‘suited, appropriate’): from Latin aptus ‘fitted’, past participle of apere ‘fasten’.
wiktionary
From Old French apte, from Latin aptus, from obsolete apere(“to fasten, to join, to fit”), akin to apisci(“to reach, attain”); compare with Greek ἅπτειν(ἅptein, “to fasten”) and Sanskrit आप्त(āpta, “fit”), from आप्(āp, “to reach, attain”).
Clipping of apartment.
etymonline
apt (adj.)
mid-14c., "inclined, disposed;" late 14c., "suited, fitted, adapted, possessing the necessary qualities for the purpose," from Old French ate "fitting, suitable, appropriate" (13c., Modern French apte), or directly from Latin aptus "fit, suited, proper, appropriate," adjectival use of past participle of *apere "to attach, join, tie to," from PIE root *ap- (1) "to grasp, take, reach" (source also of Sanskrit apnoti "he reaches," Latin apisci "to reach after, attain," Hittite epmi "I seize"). Elliptical sense of "becoming, appropriate" is from 1560s.
