Portmanteau

A portmanteau (pronounced /pɔrtmænˈtoʊ/ ( listen), plural: portmanteaus or portmanteaux) or portmanteau word is used broadly to mean a blend of two (or more) words or morphemes and their meanings into one new word.[1][2][3] In linguistics fields, a portmanteau is defined as a blend of two or more function words.

Reference: http://en.wikipedia.org/wiki/Portmanteau