"I want a Viking to scare you. I don't want a Viking to say, [Tony Curtis style] "I'm going to die with a sword in my hand." I don't want to hear that. It pulls the rug out from under you. I want to see somebody who I have never seen before speaking low guttural German who scares the living sh*t out of me coming up to my house. What is that like? What would that have been like?" Gibson is unsure whether it'll be in Old Norse or Old English. "Whatever the 9th century had to offer. I'm going to give you real." Leonardo DiCaprio is going to have his work cut out for him. But hey, English majors survive this every year, and they pay for the privilege of pronouncing it.
If the movie is really dealing with the 9th century Viking raids, then the Vikings will speak Old Norse. If the film decides to deal with them raiding and pillaging England or Ireland, then all their victims can speak Old English (which was awfully similar even before the Norse lent them all the case endings) and Gaelic just to make things extra interesting. As translating Old English was the last thing I did before fleeing for cinematic lands, this thrills me to no end. Just hearing old Germanic language puts you into the cold chill of the early middle ages (I've embedded the classic example of Beowulf below. I can't find any spoken Old Norse online. The closest equivalent is allegedly modern Icelandic, so maybe just listen to some Sigur Ros), so an entire costumed film set to the language would be like having a time machine. I can't wait.