Portmanteau

Portmanteau (pronounced pawrt-man-toh)

(1) A case or bag to carry clothing in while traveling, made usually from stiff leather, hinged at the back so as to open out into two compartments

(2) A word created by blending two or more existing words.

1580s (for the travelling case (flexible traveling case or bag for clothes and other necessaries)): From the Middle French portemanteau (travelling bag, literally "(it) carries (the) cloak").  The original meaning from the 1540s was “court official who carried a prince's mantle" from porte, (imperative of porter (to carry) + manteau (cloak)).  The correct plural is portmanteaux but in modern English use, portmanteaus (following the conventions for constructing plurals in English) is now more common.  In the nineteenth century, the word was sometimes Englished as portmantle, a use long extinct.  The notion of the portmanteau word (word blending the sound of two different words) was coined by Lewis Carroll (pen-name of Charles L. Dodgson; 1832-1898) in 1871 for the constructions he invented for Alice Through the Looking-Glass such as Jabberwocky, his poem about the fabulous beast the Jabberwock.  Portmanteau in this sense has existed as a noun since 1872.

Vintage Louis Vuitton Portmanteau, typically circa US$50-80,000 depending on condition.

A portmanteau word, a linguistic blend, differs from contractions and compounds.  Contractions are formed from words that would otherwise appear together in sequence, such as do + not to make don't, whereas a portmanteau word is joins two or more words that relate to the one contractual theme.  A compound word is merely the joining for words in their original form (eg under + statement) without any truncation of the blended words.  Portmanteau words (eg breakfast & lunch to create brunch) always modifies at least one of the original stems.

Lindsay Lohan's handy moniker Lilo (the construct being Li(ndsay) + Lo(han) and it's used sometimes as LiLo) is a portmanteau word.

The word portmanteau was first used in this sense by Lewis Carroll in Alice Through the Looking-Glass (1871) where the concept is helpfully explained by Humpty Dumpty.  Less erudite but just as amusing was the creation of refudiate by Sarah Palin when she got confused and conflated refute and repudiate although it’s unclear whether she knew the meaning of either.  Even those created or used by more literate folk are not always accepted.  Irregardless (portmanteau of regardless and irrespective) seems to stir strong feelings of antipathy in pedants who generally won’t accept it even as a non-standard form and insist it’s simply wrong.  Other languages also create blended forms as needed.  The title of Emile Habibi’s 1974 novel was translated from Arabic utashaʔim (pessimist) + mutafaʔil (optimist) into English as The Pessoptimist.  Arabic linguistic traditions however prefer acronyms and compounds which sometimes overlap.  The group known variously as ISIL or ISIS (although they came to prefer "caliphate" or "Islamic State" (IS)) first adopted the name ad-Dawlah al-Islāmiyah fī 'l-ʿIrāq wa-sh-Shām (Islamic State if Iraq and the Levant) which is usually written as Daesh or Da'ish.  IS think this derogatory as it resembles the Arabic words daes (one who tramples underfoot) and dāhis (those who sows discord).  IS threatened to punish those who use Daesh or Da'ish with a public flogging; repeat offenders promised the cutting out of the tongue.

In the manufacture of big words, English is unlikely ever to match the Germans.  Until changes in EU regulations rendered it obsolete, the longest word in the Fourth Reich was rindfleischetikettierungsueberwachungsaufgabenuebertragungsgesetz (law delegating beef label monitoring).  Currently, the longest word accepted by German dictionaries is kraftfahrzeughaftpflichtversicherung (automobile liability insurance), editors rejecting donaudampfschifffahrtsgesellschaftskapitaenswitwe (widow of a Danube steamboat company captain) because of rarity of use.