Garudapurana 3.28.47

3.28.47

kṛṣṇāvatāre droṇanāmā babhūva aṃbhojajāveśayuto bṛhasyapatiḥ /
yasmāddoṇātsaṃbhabhūva guruśca tasmādasau droṇasaṃjño babhūva //

In the Kṛṣṇa incarnation, Bṛhaspati became the one named Droṇa, endowed with the possession by the lotus-born [Brahmā];
because the preceptor was born from a wooden trough (droṇa), therefore he had the name Droṇa.