eggcorn or egg corns are the mistaken name for acorns. The term means any long held mistaken saying.
eg 1. - Crimean River - "Oh, you have problems, crimean river" (mistaken thought that somthing bad happend during the crimean war, by a river!)
mentioned on Adam and Joe's radio show.
Egg Corn eg 2. - My condiments to the chef - "That food was lovely, my condiments to the chef" (mistaken thought that: If food is really good then you send the unneeded seasonings back to the chef!)