Thomas the Rhymer Child Ballad 37 is traceable back at least as far as the 13th century. It deals with the supernatural subject matter of fairy-folk. The theme of this song is also closely related to another song following the same general topical lines, that of Tam Lin. Its more general theme relates to temptation and mortal pleasures.
There are several different variants of the story of Thomas Rhymer, most having the same basic theme that Thomas either kissed or had sex with the Queen of Fairyland and either rode with her or was otherwise transported to Fairyland. One version relates that she changed into a hag immediately after sleeping with him, as some sort of a punishment to him, but returned to her originally beautiful state when they neared her castle, where her husband lived. Thomas stayed at a party in the castle, until she told him to return with her, coming into the mortal realm only to realise seven years had passed (a significant number in magic). He asked for a token to remember the Queen by, and was then offered the choice of being a harper or a prophet, and chose the latter. He became known as true Thomas, because he could not tell a lie, and was popularly supposed to have prophesised many great events in Scottish history. His gift of prophecy seems to have been related to that of poetry, as Thomas was a noted poet (hence, "Rhymer"), and was supposed to have written the ballad of St Tristrem. After a number of years had passed Thomas returned to fairyland, from whence he has not yet returned.
Thomas of Ercildoune was an historical figure, as records have been found naming his son as the son of "Thomas Rymour of Ercildoune". The fifteenth century romance "Thomas of Erceldoune" with its accompanying prophcies is clearly related to the ballad, though the exact nature of the relationship is not clear.
The song has been recorded in recent times by folk-rock band Steeleye Span.
