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

(21) Then they debated one with another what they must do, and they kept their counsel secret.

(22) With hearts preoccupied. And they confer in secret. The wrong-doers say: Is this other than a mortal like you? Will ye then succumb to magic when ye see (it)?

(23) Those who fear their Lord in secret and who dread the Hour (of doom).

(24) Say (unto them, O Muhammad): He who knoweth the secret of the heavens and the earth hath revealed it. Lo! He ever is Forgiving, Merciful.

(25) And no burdened soul can bear another's burden, and if one heavy laden crieth for (help with) his load, naught of it will be lifted even though he (unto whom he crieth) be of kin. Thou warnest only those who fear their Lord in secret, and have established worship. He who groweth (in goodness), groweth only for himself, (he cannot by his merit redeem others). Unto Allah is the journeying.

(26) Lo! those who read the Scripture of Allah, and establish worship, and spend of that which We have bestowed on them secretly and openly, they look forward to imperishable gain,

(27) Lo! Allah is the Knower of the Unseen of the heavens and the earth. Lo! He is Aware of the secret of (men's) breasts.

(28) Thou warnest only him who followeth the Reminder and feareth the Beneficent in secret. To him bear tidings of forgiveness and a rich reward.

(29) Or deem they that We cannot hear their secret thoughts and private confidences? Nay, but Our envoys, present with them, do record.

(30) That is because they say unto those who hate what Allah hath revealed: We will obey you in some matters; and Allah knoweth their secret talk.