Merriam-Webster's Collegiate® Dictionary, 11th Edition
BLUNDER
I. verb (blundered; blundering)
Etymology: Middle English blundren, probably of Scandinavian origin; akin to Old Norse blunda to shut one's eyes, doze, Norwegian dialect blundra
Date: 14th century
intransitive verb to move unsteadily or confusedly, to make a mistake through stupidity, ignorance, or carelessness, transitive verb to utter stupidly, confusedly, or thoughtlessly, to make a stupid, careless, or thoughtless mistake in, blunderer noun blunderingly adverb
II. noun
Date: 1693
a gross error or mistake resulting usually from stupidity, ignorance, or carelessness, see: error