It's pronounced jellyhorn. Since back before crota pplz were jello that they didn't have one.

Of course you are. The correct pronunciation is the one that correctly communicates what you are thinking to the person who is listening. We are talking about a word that was used first in an widley dispersed old-norse oral tradition, later written down in medieval Icelandic in a latin script and is now being spoken by people all over the world with vastly different phonological experiences. So whether you use the a Hard G, or voiced fricative and consinantal i or any one of a number of variants, we still know what you are talking about, and the rest is just people trying one-up.

You're allowed to be incorrect as well.