Origin of dejectMiddle English dejecten from Classical Latin dejectus, past participle of dejicere from de-, down + jacere, to throw: see jet
transitive verbde·ject·ed, de·ject·ing, de·jects
Origin of dejectMiddle English dejecten from Latin dēicere dēiect- to cast down dē- de- iacere to throw ; see yē- in Indo-European roots.
(third-person singular simple present dejects, present participle dejecting, simple past and past participle dejected)
From Old French dejeter, from Latin deicere (“to throw down”).