大方廣佛華嚴經搜玄分齊通智方軌 3.17

3.17

一釋名者，得出世間智方便善巧，能度難度，故名難勝地。

First, regarding the explanation of the name: having attained supramundane wisdom and skillful means, one can cross over what is difficult to cross; therefore it is called the Bhūmi Difficult to Conquer (Sudurjayā-bhūmi).