 The dodo 's significance as one of the best @-@ known extinct animals and its singular appearance led to its use in literature and popular culture as a symbol of an outdated concept or object , as in the expression " dead as a dodo , " which has come to mean unquestionably dead or obsolete . Similarly , the phrase " to go the way of the dodo " means to become extinct or obsolete , to fall out of common usage or practice , or to become a thing of the past . " Dodo " is also a slang term for a stupid , dull @-@ witted person , as it was supposedly stupid and easily caught . 
