What's it called--not an acronym--when the beginning of two or more words are put together to form a word?

Question

Examples: The California Department of Transportation is commonly referred to as CalTrans. The California Institute of Technology is called Caltech. I think there's a name for this type of abbreviation, but I can't remember it.

Answer 1

A portmanteau

(plural: portmanteaus or portmanteaux) or blend is a word that fuses two or more words or parts of words to give a combined meaning. Like SPORK from spoon/fork.

A common usage of portmanteau refers to a word that is formed by combining both sounds and meanings from two or more words

Answer 2

paraphrase