Bṛhadāraṇyaka Upaniṣad ("Great Forest Teaching") 1.2.4

1.2.4

so'kāmayata dvitīyo ma ātmā jāyeteti sa manasā vācaṃ mithunam̐ samabhavadaśanāyā mṛtyustadyadreta āsītsa saṃvatsaro'bhavat | na ha purā tataḥ saṃvatsara āsa tametāvantaṃ kālamabibhaḥ | yāvānsaṃvatsarastametāvataḥ kālasya parastādasṛjata taṃ jātamabhivyādadātsa bhāṇakarotsaiva vāgabhavat

He desired, 'Let a second body be born of me,' and he (Death or Hunger) embraced Speech in his mind. Then the seed became the year. Before that time there was no year. Speech bore him so long as a year, and after that time sent him forth. Then when he was born, he (Death) opened his mouth, as if to swallow him. He cried Bhân! and that became speech.