Thomas the Rhymer
Thomas Learmont, of Ercildoune, a Scotchman, in the reign of Alexander III., and contemporary with Wallace. He is also called Thomas of Ercildoune. Sir Walter Scott calls him the “Merlin of Scotland.” He was magician, prophet, and poet, and is to return again to earth at some future time when Shrove Tuesday and Good Friday change places.
Care must be taken not to confound “Thomas the Rhymer” with Thomas Rymer, the historiographer and compiler of the Foedera.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894