Shoo-in

A shoo-in is a certain winner, an American expression that dates from the late 1920s and which originated from horseracing. It derives from 'shoo' the word used to force animals like horses to go away and so run faster. Thus, a horse that was 'shoo-ed' or urged towards the finishing post was a certain winner. More recently, it is often misspelt as 'shoe-in' and, with time, this may eventually become the accepted spelling.