deleterious adj.

1640s, "noxious, poisonous," from Medieval Latin deleterius, from Greek dēlētērios "noxious," from dēlētēr "destroyer," from dēlēisthai "to hurt, injure," of which Beekes writes, "the verb is probably non-IE, i.e. Pre-Greek." From 1823 as "mentally or morally hurtful or injurious." Related: Deleteriously; deleteriousness.