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

(11) Those in whose hearts is a disease - thou seest how eagerly they run about amongst them, saying: "We do fear lest a change of fortune bring us disaster." Ah! perhaps Allah will give (thee) victory, or a decision according to His will. Then will they repent of the thoughts which they secretly harboured in their hearts.

(12) Eschew all sin, open or secret: those who earn sin will get due recompense for their "earnings."

(13) Say: "Come, I will rehearse what Allah hath (really) prohibited you from": Join not anything as equal with Him; be good to your parents; kill not your children on a plea of want;- We provide sustenance for you and for them;- come not nigh to shameful deeds. Whether open or secret; take not life, which Allah hath made sacred, except by way of justice and law: thus doth He command you, that ye may learn wisdom.

(14) Say: the things that my Lord hath indeed forbidden are: shameful deeds, whether open or secret; sins and trespasses against truth or reason; assigning of partners to Allah, for which He hath given no authority; and saying things about Allah of which ye have no knowledge.

(15) Remember in thy dream Allah showed them to thee as few: if He had shown them to thee as many, ye would surely have been discouraged, and ye would surely have disputed in (your) decision; but Allah saved (you): for He knoweth well the (secrets) of (all) hearts.

(16) Know they not that Allah doth know their secret (thoughts) and their secret counsels, and that Allah knoweth well all things unseen?

(17) Behold! they fold up their hearts, that they may lie hid from Him! Ah even when they cover themselves with their garments, He knoweth what they conceal, and what they reveal: for He knoweth well the (inmost secrets) of the hearts.

(18) To Allah do belong the unseen (secrets) of the heavens and the earth, and to Him goeth back every affair (for decision): then worship Him, and put thy trust in Him: and thy Lord is not unmindful of aught that ye do.

(19) They said: "If he steals, there was a brother of his who did steal before (him)." But these things did Joseph keep locked in his heart, revealing not the secrets to them. He (simply) said (to himself): "Ye are the worse situated; and Allah knoweth best the truth of what ye assert!"

(20) Those who patiently persevere, seeking the countenance of their Lord; Establish regular prayers; spend, out of (the gifts) We have bestowed for their sustenance, secretly and openly; and turn off Evil with good: for such there is the final attainment of the (eternal) home,-