solecism

Dictionary.com/Word of the Day: solecism:
solecism \SOL-uh-siz-uhm\, noun:
1. A nonstandard usage or grammatical construction; also, a minor blunder in speech.
2. A breach of good manners or etiquette.
3. Any inconsistency, mistake, or impropriety

Solecism comes from Latin soloecismus, from Greek soloikizein, "to speak incorrectly," from soloikos, "speaking incorrectly," literally, "an inhabitant of Soloi," a city in ancient Cilicia where a dialect regarded as substandard was spoken.