It is true that just because humans know a word in their brains, they do not always know how to say it with their mouths.
“Jökull” is a word that many people know because of my volcano. It means “glacier”.
As you can see on this picture of me, I have many jöklar for you to look at, and, if you are very strong, you can also climb on some of them.
Many of the men living on me are also called Jökull. Here is one of them. You can say halló to him.