俱舍論記 23.123

23.123

「諸無漏道至說名預流」者，釋預流名。諸無漏道總名為流，由此無漏為因，流趣涅槃故。「預」言為顯最初至得義，彼預無漏法流中故，說名預流。

"All anāsrava paths [...] are called srotaāpanna" explains the name srotaāpanna. All anāsrava paths are collectively called the "stream" (srotas), because with this anāsrava [path] as cause, they stream toward nirvāṇa. The word "enterer" (āpanna) is to indicate the meaning of initial attainment; because they have entered into the stream of anāsrava dharmas, they are called srotaāpanna (stream-enterers).