Portmanteau word

A portmanteau word combines both the sounds and the meanings of its components, as in smog, which mixes together smoke and fog.

Wittertainment is in itself a portmanteau word. However, the best of this ilk has been definitely proved to be (well Susie Dent said it so it must be true) Chortle which was invented by Lewis Carroll and is a blend of chuckle and snort.