Horseleap (Irish: Baile Átha an Urchair) is a town situated upon the Offaly, Westmeath county border in Ireland, along the R446, formerly the main Dublin to Galway road. The village itself possesses a church, primary school, a garden centre, a pub, and a petrol station. Horseleap dates back to the 12th century and is steeped in Ui Neill, Geoghegan history.

The village's Irish name (Baile Átha an Urchair or Áth an Urchair) was historically anglicised as Ballanurcher, Athnurcher and Ardnurcher. The name probably derives from the legend that Conchobar mac Nessa was killed here.

According to tradition, the English name - Horseleap - originated in an incident in which a member of the De Lacy family was forced to flee on horseback from the Mac Geoghegans. On approaching his castle and discovering that the drawbridge was raised, he jumped the castle's moat on horseback.

The battle of Ardnocher took place here in 1329 between the forces of Thomas Butler and William Mac Geoghegan. Mac Geoghegan forces won and Butler and many of his soldiers were killed.

Dark horse is a term used to describe a little-known person or thing that emerges to prominence, especially in a competition of some sort or a contestant that seems unlikely to succeed.

The term began as horse racing parlance. A dark horse is a race horse that is not known to gamblers and thus is difficult to place betting odds on.

The earliest-known use of the phrase is in Benjamin Disraeli's novel The Young Duke (1831). Disraeli's protagonist, the Duke of St. James, attends a horse race with a surprise finish: "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."

The term has been used politically in such countries as Peru, Philippines and United States.

Politically, the term reached America in the nineteenth century when it was first applied to James K. Polk, a relatively unknown Tennessee Democrat who won the Democratic Party's 1844 presidential nomination over a host of better-known candidates. Polk won the nomination on the ninth ballot, and went on to win the presidential election.