Nothing to chortle at
It seems as though we have Lewis Carroll to thank for the word chortle. He coined it in his poem Jabberwocky, apparently as a blend of the words snort and chuckle. We also have him to thank for the application of the word portmanteau to linguistic forms that contain multiple parts–though the morphologist’s use of the word usually refers to morphemes with specifications across multiple grammatical categories (number/gender/tense/etc.), while in common (?) parlance a portmanteau word is a blend of multiple words, like chortle.