SB 9.14.14

tasyātma-yonir akṛta
 budha ity abhidhāṁ nṛpa
buddhyā gambhīrayā yena
 putreṇāpoḍurāṇ mudam
Word for word: 
tasya — of the child; ātma-yoniḥ — Lord Brahmā; akṛta — made; budhaḥ — Budha; iti — thus; abhidhām — the name; nṛpa — O King Parīkṣit; buddhyā — by intelligence; gambhīrayā — very deeply situated; yena — by whom; putreṇa — by such a son; āpa — he got; uḍurāṭ — the moon-god; mudam — jubilation.
Translation: 
O Mahārāja Parīkṣit, when Lord Brahmā saw that the child was deeply intelligent, he gave the child the name Budha. The moon-god, the ruler of the stars, enjoyed great jubilation because of this son.