The word(s) "secret" appears 51 time(s) in 49 verse(s) in Quran in Abdullah Yusuf Ali translation.

(21) Speak to my servants who have believed, that they may establish regular prayers, and spend (in charity) out of the sustenance we have given them, secretly and openly, before the coming of a Day in which there will be neither mutual bargaining nor befriending.

(22) Say: "Allah knows best how long they stayed: with Him is (the knowledge of) the secrets of the heavens and the earth: how clearly He sees, how finely He hears (everything)! They have no protector other than Him; nor does He share His Command with any person whatsoever.

(23) Behold! he cried to his Lord in secret,

(24) If thou pronounce the word aloud, (it is no matter): for verily He knoweth what is secret and what is yet more hidden.

(25) So they disputed, one with another, over their affair, but they kept their talk secret.

(26) Those who fear their Lord in their most secret thoughts, and who hold the Hour (of Judgment) in awe.

(27) They said: "Swear a mutual oath by Allah that we shall make a secret night attack on him and his people, and that we shall then say to his heir (when he seeks vengeance): 'We were not present at the slaughter of his people, and we are positively telling the truth.'"

(28) Those who rehearse the Book of Allah, establish regular Prayer, and spend (in Charity) out of what We have provided for them, secretly and openly, hope for a commerce that will never fail:

(29) What! Do they say, "He has forged a falsehood against Allah"? But if Allah willed, He could seal up thy heart. And Allah blots out Vanity, and proves the Truth by His Words. For He knows well the secrets of all hearts.

(30) Or do they think that We hear not their secrets and their private counsels? Indeed (We do), and Our messengers are by them, to record.