大方廣圓覺修多羅了義經略疏 2.465

2.465

亦名三摩鉢底，此云等至，等持之中能至勝位故。又等謂齊等，離沈掉故。至謂至到，到勝定故。故前有如幻三昧。

Also called samāpatti; this is translated as 'equipoised attainment' (dengzhi). Because within meditative equipoise (samāhita) one can attain the supreme stage. Furthermore, 'equal' (deng) means balanced, free from torpor and restlessness. 'Attainment' (zhi) means reaching, reaching the supreme absorption. Therefore earlier there was the illusion-like samādhi.