These are called "wolf trees", trees whose lumber has knots that make the wood less desirable.
This WWII poster warning people to destroy "wolf trees" is interesting:
A wolf tree is a large tree that usually developed in the open with an undesirable form (from a logger's perspective) since the trunks aren't good for lumber and they shade out nearby younger trees.
Wolf trees are generally culled for firewood to make space for trees that will have straight branchless trunks.