Jaiminīya Upaniṣad Brāhmaṇa 1.4.2

1.4.2

etaṃ ha vā etaṃ nyaṅgam anu garbha iti
yad bha iti strīṇām prajananaṃ nigacchati tasmāt tato brāhmaṇa ṛṣikalpo jāyate 'tivyādhī rājanyaś śūraḥ /

Following this very inserted syllable, the embryo [comes into being].
When it reaches the generative organ of women with 'bha', from that is born a brāhmaṇa equal to a ṛṣi, or a nobleman who is an archer and a hero.