ἐνθύμιον
From LSJ
Τοὺς τῆς φύσεως οὐκ ἔστι λανθάνειν (μανθάνειν) νόμους → Legibus naturae non potest evadier → Naturgesetze keiner insgeheim verletzt
English (Woodhouse)
scruple, point of conscience, qualm of conscience, something that weighs on one's conscience, twinge of conscience