back-formation

CIDE DICTIONARY

back-formation, n. 

•  a word invented (usually unwittingly by subtracting an affix) on the assumption that a familiar word derives from it, such as emote from emotion.  [WordNet 1.5]
•  the process of inventing a back-formation{1}.  [PJC]

ROGET THESAURUS

back-formation

Neologism

N neology, neologism, newfangled expression, nonce expression, back-formation, caconym, barbarism, archaism, black letter, monkish Latin, corruption, missaying, malapropism, antiphrasis, pun, paranomasia, play upon words, word play, double- entendre, palindrome, paragram, anagram, clinch, abuse of language, abuse of terms, dialect, brogue, idiom, accent, patois, provincialism, regionalism, localism, broken English, lingua franca, Anglicism, Briticism, Gallicism, Scotticism, Hibernicism, Americanism, Gypsy lingo, Romany, pidgin, pidgin English, pigeon English, Volapuk, Chinook, Esperanto, Hindustani, kitchen Kaffir, dog Latin, macaronics, gibberish, confusion of tongues, Babel, babu English, chi-chi, figure of speech, byword, colloquialism, informal speech, informal language, substandard language, vernacular, vulgar language, obscene language, obscenity, vulgarity, jargon, technical terms, technicality, lingo, slang, cant, argot, St. Gile's Greek, thieves' Latin, peddler's French, flash tongue, Billingsgate, Wall Street slang, pseudology, pseudonym, Mr, So-and-so, wha d'ye call 'em, whatchacallim, what's his name, thingummy, thingumbob, je ne sais quoi, neologist, coiner of words, neologic, neological, archaic, obsolete, colloquial, Anglice.