A kenning is a way of describing something without using its name. It usually consists of two words that describe a feature of the noun (the person, animal or object) being described.
A kenning poem consists of several kennings describing the same noun. It is a bit like a riddle, as the reader has to work out what is being described. What do you think this kenning poem describes?
Did you work out that it is a cat?
Kennings were used a lot in Old English and Norse poetry and there are many examples in the famous Anglo-Saxon poem Beowulf.