說無垢稱經疏 4.47

4.47

贊曰：自下第十，命阿難陀，初命、後辭。此命也。阿難陀者，此云慶喜。釋迦成道，人天慶喜，當此夜生，因以為稱。後年二十，方始出家。佛法皆聞。為佛侍者，親而且侍，故今命之。

Commentary: From here down is the tenth, commanding Ānanda: first the command, then the declining. This is the command. 'Ānanda' is translated here as 'Rejoicing Joy'. When Śākyamuni attained awakening, humans and devas rejoiced; he was born on that very night, and was therefore given this name. Later, at the age of twenty, he finally renounced. He heard all of the Buddha's teachings. Being the Buddha's attendant, intimate and serving him, [the Buddha] now commands him.