The word(s) "secret" appears 40 time(s) in 40 verse(s) in Quran in Muhammad Pickthal translation.

(11) (O mankind!) Call upon your Lord humbly and in secret. Lo! He loveth not aggressors.

(12) Know they not that Allah knoweth both their secret and the thought that they confide, and that Allah is the Knower of Things Hidden?

(13) (Then Joseph said: I asked for) this, that he (my lord) may know that I betrayed him not in secret, and that surely Allah guideth not the snare of the betrayers.

(14) They said: If he stealeth, a brother of his stole before. But Joseph kept it secret in his soul and revealed it not unto them. He said (within himself): Ye are in worse case, and Allah knoweth best (the truth of) that which ye allege.

(15) Such as persevere in seeking their Lord's Countenance and are regular in prayer and spend of that which We bestow upon them secretly and openly, and overcome evil with good. Theirs will be the sequel of the (heavenly) Home,

(16) Tell My bondmen who believe to establish worship and spend of that which We have given them, secretly and publicly, before a day cometh wherein there will be neither traffick nor befriending.

(17) Allah coineth a similitude: (on the one hand) a (mere) chattel slave, who hath control of nothing, and (on the other hand) one on whom we have bestowed a fair provision from Us, and he spendeth thereof secretly and openly. Are they equal? Praise be to Allah! But most of them know not.

(18) We are Best Aware of what they wish to hear when they give ear to thee and when they take secret counsel, when the evil-doers say: Ye follow but a man bewitched.

(19) When he cried unto his Lord a cry in secret,

(20) And if thou speakest aloud, then lo! He knoweth the secret (thought) and (that which is yet) more hidden.