There are many mysteries found in the Bible. Of course, with modern software, one can do an instant word search to show all the places a certain word was used, whether translated from Hebrew or Greek manuscripts. One interesting word that scholars debate the meaning of is the word "selah" - which is found in only two books of the Bible, it appears three times in the third chapter of Habakkuk, but a whopping 71 time in Psalms, yet no one can tell us definitively what it actually means. Here's a bit about it here: https://www.gotquestions.org/selah.html
Any other mystery words in the Bible you've come across?