俱舍論記 10.116

10.116

「傳說喜等至數遊行故」者，答。前解喜等以意為近緣，於諸境中數遊行故，故名意近行。後解喜等與意為近緣，令意於境數行故，故名意近行。

Regarding "It is traditionally said: joy and the rest … frequently roaming": the answer. The first explanation is that joy and the rest take the mind as their proximate condition and frequently roam among objects, hence they are called mental applications (manovicāra). The second explanation is that joy and the rest serve as proximate conditions for the mind, causing the mind to frequently apply itself to objects, hence they are called mental applications.