A portmanteau (or portmanteau word) is a blend of two (or more) words into one new word. It typically combines both sounds and meanings, as in smog, coined by blending smoke and fog.
The word “portmanteau” was first used in this sense by Lewis Carroll in the book Through the Looking-Glass (1871), in which Humpty Dumpty explains to Alice the coinage of the unusual words in Jabberwocky,where “slithy” means “lithe and slimy” and “mimsy” is “flimsy and miserable”. Humpty Dumpty explains the practice of combining words in various ways by telling Alice, “You see it’s like a portmanteau — there are two meanings packed up into one word.”
Portmanteaus can be seen everywhere: in every day words, technology, science, marketing, the arts, politics, and company and brand names. Examples include: brunch (breakfast + lunch), cyborg (cybernetic + organism), fantabulous (fantastic + fabulous), pixel (pixel + element), blog (web + log), wikipedia (wiki + encyclopedia), Bennifer (Ben Affleck + Jennifer Aniston), and countless others. (wiki, list of portmanteaux)