Revākhaṇḍa ascribed to the Vāyupurāṇa (RKV) 230.13

230.13

nāmanirvacanaṃ tadvattathā kalpasamudbhavāḥ /
ekaviṃśatikalpānāṃ tadvannāmānukīrtanam //

likewise the etymological explanation of the name, the origins during the kalpas, / and the enumeration of the names across the twenty-one kalpas;