I agree it's a portmanteau. What I keep asking myself is what two words portmanteau comes from, te-he.
In fact, the name 'portmanteau' comes from the master of them himself, the author of Through the Looking Glass and Alice in W., Lewis Carroll; something about a leather suitcase having two compartments I believe.
Anyway here are a few more:
twirl = twist & swirl
motel = motor hotel
.....