Shatapatha Brahmana 9.1.2.22

9.1.2.22

tāḥ prajāpatimabruvan | yadvai naḥ kamabhūdavāktadagāditi so 'bravīdeṣa va etasya vanaspatirvettviti vettu saṃvettu so 'ha vai taṃ vetasa ityācakṣate paro 'kṣam paro 'kṣakāmā hi devā atha yadabruvannavāṅtaḥ kamagāditi tā avākkā abhavannavākkā ha vai tā avakā ityācakṣate paro 'kṣam paro 'kṣakāmā hi devāstā haitāstrayya āpo yanmaṇḍūko 'vakā vetasaśākhaitābhirevainametattrayībhiradbhiḥ śamayati

They (the waters) said to Pragâpati, 'Whatever moisture we had, has gone down.' He said, 'This tree shall know it!'--he shall know (vettu), he shall taste it (sam vettu)--that one, indeed, they mystically call 'vetasa' (bamboo), for the gods love the mystic. And because they said, 'Down (avâk) has gone our moisture (ka),' they became avâkkâs;--'avâkkâs,' they mystically call 'avakâs (lotuses),' for the gods love the mystic. These, then, are those three kinds of water, to wit, the frog, the lotus-flower, and the bamboo-shoot: by means of these three kinds of water he appeases him.