教觀綱宗 1.20

1.20

祕密亦有二義：一、祕密教，謂於前四時中，或為彼人說頓，為此人說漸等，彼此互不相知，各自得益（《法華》正直捨方便，但說無上道，故非祕密）；二、祕密呪，謂一切陀羅尼章句，即五時教中，皆悉有之。

Secret also has two meanings: First, the secret teaching, meaning that in the preceding four periods, expounding sudden for that person while expounding gradual for this person, etc., where each was unaware of the other and each derived benefit. (The Saddharmapuṇḍarīka directly discards expedients and speaks only of the unsurpassed Way, hence it is not secret.) Second, secret dhāraṇī, meaning all verses of dhāraṇī, which are present throughout the teachings of all five periods.