Answer:
The best answer to the question: What literary device is the term war gear, would be: It is a kenning.
Step-by-step explanation:
This literary device, which is used as a figure of speech as well, is very common particularly in Old Norse and Old English poetry. And this particular kenning, war gear, is part of Beowulf, a poem that has been known for being rich in this type of figurative language.
A kenning is described as a literary device in which a compound of two words, are used to form poetic expressions, often metaphorical, and that make relation to either a person, or a thing. They tend to make reference to words, or concepts, that are more simple without the use of these literary devices.