A portmanteau word is made of other words, or parts of words. It comes from putting two (or more) other words together, like motel, from motor and hotel.
Portmanteau originally meant a type of suitcase with two separate parts for storage. The first use as a word combination appeared in Lewis Carroll's book Through the Looking-Glass. There Humpty Dumpty explains that some of the unusual words in Jabberwocky are other words packed together into one word, as two parts of a portmanteau suitcase are packed together.
Images for kids
Portmanteau word Facts for Kids. Kiddle Encyclopedia.