http://en.wiktionary.org/wiki/solecism
Solecism, n.
1. Error in the use of language, especially an error concerning etiquette.
2. In written language, the intentional use of misspelling and/or incorrect grammar to affect the vernacular of a particular dialect.
3. Any faux pas involving a transgression against the norms of expected behavior.
[From the Greek Σολοικισμος (soloikismos); from Σολοικος (Soloikos), speaking incorrectly; from Σολοι (Soloi), an ancient Athenian colony in Cilicia whose inhabitants spoke a dialect that Athenians regarded as a corrupted and barbarous form of Attic.]