user23952: 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?

user471: Apparently it comes from popular legends.
From the Encyclopedia Brittanica entry on Nagarjuna:

Nagarjuna is particularly associated with the Prajnaparamita
(“Perfection of Wisdom”) sutras in this corpus. According to legend,
he retrieved from the bottom of the sea a perfection-of-wisdom sutra
that the Buddha had entrusted to the king of the nagas (water deities)
for safekeeping.

From the New World Encyclopedia entry on Nagarjuna:

Popular legends of Nagarjuna's life state that he traveled deep into
the earth through his meditative powers (siddhi) to the lair of the
nāga king, who had been entrusted by the Buddha with the Prajñā
Pāramitā Sutras. Seeing that Nagarjuna was the one prophesied by
Gautama who would "give vast and perfect explanations of the Buddha's
teachings" (Gyamtso 2003, ix), he gave these texts to him to bring
back to the surface. This story is used to explain the first part of
his name (the second, arjuna, meaning “bright,” “shining,” or
“silver”), his close association with the Prajñā Pāramitā Sutras, and
his depiction in iconography with snakes extending over his head.


23952: <p>I've seen this glossary entry in a couple of places:</p>
<p><em>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 <strong>secretly entrusted to underground serpents</strong>. The Theravāda school of today is a descendent of the Hīnayāna.</em></p>
<p>Does anyone know where this claim about the origin of Mahāyāna texts comes from?</p>
 471: <p>Apparently it comes from popular legends.</p>
<p>From the Encyclopedia Brittanica entry on <a href="https://www.britannica.com/biography/Nagarjuna" rel="nofollow noreferrer">Nagarjuna</a>:</p>
<blockquote>
<p>Nagarjuna is particularly associated with the <em>Prajnaparamita</em>
(“Perfection of Wisdom”) sutras in this corpus. According to <strong>legend</strong>,
he retrieved from the bottom of the sea a perfection-of-wisdom sutra
that the Buddha had entrusted to the king of the <em>nagas</em> (water deities)
for safekeeping.</p>
</blockquote>
<p>From the New World Encyclopedia entry on <a href="https://www.newworldencyclopedia.org/entry/Nagarjuna" rel="nofollow noreferrer">Nagarjuna</a>:</p>
<blockquote>
<p><strong>Popular legends</strong> of Nagarjuna's life state that he traveled deep into
the earth through his meditative powers (<em>siddhi</em>) to the lair of the
<em>nāga</em> king, who had been entrusted by the Buddha with the <em>Prajñā
Pāramitā</em> Sutras. Seeing that Nagarjuna was the one prophesied by
Gautama who would &quot;give vast and perfect explanations of the Buddha's
teachings&quot; (<a href="https://rads.stackoverflow.com/amzn/click/com/1570629994" rel="nofollow noreferrer" rel="nofollow noreferrer">Gyamtso 2003</a>, ix), he gave these texts to him to bring
back to the surface. This story is used to explain the first part of
his name (the second, <em>arjuna</em>, meaning “bright,” “shining,” or
“silver”), his close association with the <em>Prajñā Pāramitā</em> Sutras, and
his depiction in iconography with snakes extending over his head.</p>
</blockquote>
