 The informal term " canker sore " is sometimes used , mainly in North America , either to describe this condition generally , or to refer to the individual ulcers of this condition , or mouth ulcers of any cause unrelated to this condition . The origin of the word " canker " is thought to have been influenced by Latin , Old English , Middle English and Old North French . In Latin , cancer translates to " malignant tumor " or literally " crab " ( related to the likening of sectioned tumors to the limbs of a crab ) . The closely related word in Middle English and Old North French , chancre , now more usually applied to syphilis , is also thought to be involved . Despite this etymology , aphthous stomatitis is not a form of cancer but rather entirely benign . 
