I've seen this glossary entry in a couple of places:
Hīnayāna: “Inferior Vehicle,” a pejorative term, coined by a group who called themselves followers of the Mahāyāna, the “Great Vehicle,” to denote the path of practice of those who aimed at Arahantship, rather than full Buddhahood. Hīnayānists refused to recognize the later discourses, composed by the Mahāyānists, that claimed to contain teachings that the Buddha felt were too deep for his first generation of disciples, and which he thus secretly entrusted to underground serpents. The Theravāda school of today is a descendent of the Hīnayāna.
Does anyone know where this claim about the origin of Mahāyāna texts comes from?