大方廣佛華嚴經隨疏演義鈔 86.3

86.3

In the commentary, "Fifth, expressing the deep and secret": there are briefly three meanings: first, expressing principle and wisdom, where phenomenon is identical with reality, just as the nirvāṇa of the three virtues is called the secret treasury, etc.; second, because of secret intention; third, because of possessing the three secrets.