Meaning: An individual or a team, whose abilities might not be well known, that isn't favourite to win a contest (an election, a match, a race, etc) but is fancied by some to have a chance of success.

Origin: Yet another expression with disputed origins. One version attributes it to the tale of a 19th century American who travelled the country with his seemingly average black horse, but one that was speedier than its rivals - and so, he won most of the races he ran. Thanks to his 'dark horse', the owner collected handsome prize money across America. The 19th century British Prime Minister and writer Benjamin Disraeli (1804 - 1881) is, though, generally credited with coming up with the expression. In his 1831 novel The Young Duke he wrote: "A dark horse which had never been thought of, and which the careless St James had never even observed in the list, rushed past the grandstand in sweeping triumph." Example: "I always said equestrian was the dark horse for a medal at these Games." Olympic Council of Ireland president Pat Hickey after showjumper Cian O'Connor won gold at the 2004 Games (he was, of course, later stripped of the medal).