• أَكِنَّة
• أَكْنَٰن
• أَكْنَنتُمْ
• تُكِنُّ
• مَّكْنُون

Appears 12 times in the Quran.

1. 2:235 وَلَا جُنَاحَ عَلَيْكُمْ فِيمَا عَرَّضْتُم بِهِۦ مِنْ خِطْبَةِ ٱلنِّسَآءِ أَوْ أَكْنَنتُمْ فِىٓ أَنفُسِكُمْ عَلِمَ ٱللَّهُ أَنَّكُمْ سَتَذْكُرُونَهُنَّ وَلَٰكِن لَّا تُوَاعِدُوهُنَّ سِرًّا إِلَّآ أَن تَقُولُوا۟ قَوْلًا مَّعْرُوفًا وَلَا تَعْزِمُوا۟ عُقْدَةَ ٱلنِّكَاحِ حَتَّىٰ يَبْلُغَ ٱلْكِتَٰبُ أَجَلَهُۥ وَٱعْلَمُوٓا۟ أَنَّ ٱللَّهَ يَعْلَمُ مَا فِىٓ أَنفُسِكُمْ فَٱحْذَرُوهُ وَٱعْلَمُوٓا۟ أَنَّ ٱللَّهَ غَفُورٌ حَلِيمٌ

   And there is no blame on you respecting that which you speak indirectly in the asking of (such) women in marriage or keep (the proposal) concealed within your minds; Allah knows that you win mention them, but do not give them a promise in secret unless you speak in a lawful manner, and do not confirm the marriage tie until the writing is fulfilled, and know that Allah knows what is in your minds, therefore beware of Him, and know that Allah is Forgiving, Forbearing.
   

2. 6:25 وَمِنْهُم مَّن يَسْتَمِعُ إِلَيْكَ وَجَعَلْنَا عَلَىٰ قُلُوبِهِمْ أَكِنَّةً أَن يَفْقَهُوهُ وَفِىٓ ءَاذَانِهِمْ وَقْرًا وَإِن يَرَوْا۟ كُلَّ ءَايَةٍ لَّا يُؤْمِنُوا۟ بِهَا حَتَّىٰٓ إِذَا جَآءُوكَ يُجَٰدِلُونَكَ يَقُولُ ٱلَّذِينَ كَفَرُوٓا۟ إِنْ هَٰذَآ إِلَّآ أَسَٰطِيرُ ٱلْأَوَّلِينَ

   And of them is he who hearkens to you, and We have cast veils over their hearts lest they understand it and a heaviness into their ears; and even if they see every sign they will not believe in it; so much so that when they come to you they only dispute with you; those who disbelieve say: This is naught but the stories of the ancients.
   

3. 16:81 وَٱللَّهُ جَعَلَ لَكُم مِّمَّا خَلَقَ ظِلَٰلًا وَجَعَلَ لَكُم مِّنَ ٱلْجِبَالِ أَكْنَٰنًا وَجَعَلَ لَكُمْ سَرَٰبِيلَ تَقِيكُمُ ٱلْحَرَّ وَسَرَٰبِيلَ تَقِيكُم بَأْسَكُمْ كَذَٰلِكَ يُتِمُّ نِعْمَتَهُۥ عَلَيْكُمْ لَعَلَّكُمْ تُسْلِمُونَ

   And Allah has made for you of what He has created shelters, and He has given you in the mountains places of retreat, and He has given you garments to preserve you from the heat and coats of mail to preserve you in your fighting; even thus does He complete His favor upon you, that haply you may submit.
   

4. 17:46 وَجَعَلْنَا عَلَىٰ قُلُوبِهِمْ أَكِنَّةً أَن يَفْقَهُوهُ وَفِىٓ ءَاذَانِهِمْ وَقْرًا وَإِذَا ذَكَرْتَ رَبَّكَ فِى ٱلْقُرْءَانِ وَحْدَهُۥ وَلَّوْا۟ عَلَىٰٓ أَدْبَٰرِهِمْ نُفُورًا

   And We have placed coverings on their hearts and a heaviness in their ears lest they understand it, and when you mention your Lord alone in the Quran they turn their backs in aversion.
   

5. 18:57 وَمَنْ أَظْلَمُ مِمَّن ذُكِّرَ بِـَٔايَٰتِ رَبِّهِۦ فَأَعْرَضَ عَنْهَا وَنَسِىَ مَا قَدَّمَتْ يَدَاهُ إِنَّا جَعَلْنَا عَلَىٰ قُلُوبِهِمْ أَكِنَّةً أَن يَفْقَهُوهُ وَفِىٓ ءَاذَانِهِمْ وَقْرًا وَإِن تَدْعُهُمْ إِلَى ٱلْهُدَىٰ فَلَن يَهْتَدُوٓا۟ إِذًا أَبَدًا

   And who is more unjust than he who is reminded of the communications of his Lord, then he turns away from them and forgets what his two hands have sent before? Surely We have placed veils over their hearts lest they should understand it and a heaviness in their ears; and if you call them to the guidance, they will not ever follow the right course in that case.
   

6. 27:74 وَإِنَّ رَبَّكَ لَيَعْلَمُ مَا تُكِنُّ صُدُورُهُمْ وَمَا يُعْلِنُونَ

   And most surely your Lord knows what their breasts conceal and what they manifest.
   

7. 28:69 وَرَبُّكَ يَعْلَمُ مَا تُكِنُّ صُدُورُهُمْ وَمَا يُعْلِنُونَ

   And your Lord knows what their breasts conceal and what they manifest.
   

8. 37:49 كَأَنَّهُنَّ بَيْضٌ مَّكْنُونٌ

   As if they were eggs carefully protected.
   

9. 41:5 وَقَالُوا۟ قُلُوبُنَا فِىٓ أَكِنَّةٍ مِّمَّا تَدْعُونَآ إِلَيْهِ وَفِىٓ ءَاذَانِنَا وَقْرٌ وَمِنۢ بَيْنِنَا وَبَيْنِكَ حِجَابٌ فَٱعْمَلْ إِنَّنَا عَٰمِلُونَ

   And they say: Our hearts are under coverings from that to which you call us, and there is a heaviness in our ears, and a veil hangs between us and you, so work, we too are working.
   

10. 52:24 وَيَطُوفُ عَلَيْهِمْ غِلْمَانٌ لَّهُمْ كَأَنَّهُمْ لُؤْلُؤٌ مَّكْنُونٌ

    And round them shall go boys of theirs as if they were hidden pearls.
    

11. 56:23 كَأَمْثَٰلِ ٱللُّؤْلُؤِ ٱلْمَكْنُونِ

    The like of the hidden pearls:
    

12. 56:78 فِى كِتَٰبٍ مَّكْنُونٍ

    In a book that is protected