This term or one of its cognates （vetulyaka， vetullaka， vaipulyavada， etc.） is found in a few Theravada sources， e.g. at Kathavatthu XXIII. Originally， the terms designated a pre- （possibly proto-） Mahayana doctrine that was regarded as heretical by the more orthodox. Later， some Theravada writers may have adopted it as a polemical label for Mahayana per se -- which is reminiscent of the history and use of the word 'hinayana' by certain Mahayana writers. See hinayana.