The origins of this word lie in the Anglo-Norman word meschevous, meaning ‘troublesome’, itself derived from mischief, which is made up of the prefix mis added to the word chief (from Latin caput ‘head’). Early spellings tended to preserve the Anglo-Norman original with mes: mescheffus, mescheuous and meschievous. The correct spelling today is mischievous, although many people erroneously spell it mischievious. This misspelling is prompted by a variant pronunciation with stress on the second syllable, which was a valid alternative until around 1700, but is now considered non-standard. It was recorded in a pronouncing dictionary of 1802; despite seeing the attractions of this pronunciation, the editor dismissed it as a vulgarism, concluding that: ‘In language, as in many other cases, it is safer to be wrong with the polite than right with the vulgar’.
The pronunciation of the word with 4 syllables goes back to the 15th century, when it was commonly spelled mischievious, mischeevious or mischievieous. This pronunciation is probably due to a tendency for speakers to replace the less common –ous ending with the –ious found in words like envious, furious and curious. The Oxford English Dictionary considers this spelling ‘regional, colloquial or humorous’, while Merriam-Webster suggests it derives from an attempt to invoke a ‘folksy’ association, or an echo of the word devious. Urban Dictionary is more damning in its judgement, labelling it ‘a common and disgusting mispronunciacion and/or spelling of the word mischievous’. The entry goes on to criticise attempts to legitimise such mistakes as linguistic evolution: ‘Changes like this are driven by the illiterate and the ignorant, and it is careless to embrace them. And embarrassing.’ I can’t help feeling this person’s rant would have greater force if it didn’t contain a misspelling of mispronunciation.
Searching The Guardian online brings up numerous profiles on the Soul Mates dating site in which lonely hearts proudly advertise their ‘mischievious’ sense of humour. Assuming they are not covertly hinting at their devious character, they must be hoping to appear folksy. Either way, they are presumably not looking for someone who values good spelling. The misspelling is especially common on Twitter. Perhaps its most famous appearance was in a tweet by Sally Bercow, in which she defended her ill-judged comments about Lord McAlpine as ‘mischievious not libellous’. As it turned out, her legal knowledge was just as flawed as her spelling.