1590s, "one who intends;" 1620s as "one who puts forth a claim;" agent noun from pretend (v.). Specifically of a claimant to the English throne from 1690s, especially the Old and Young Pretenders, the son and grandson of James II who asserted claims to the throne against the Hanoverians. Meaning "one who feigns, one who makes a false show, one who puts forth a claim without adequate grounds" is from 1630s.
Having been a spectator of the battle of the Boyne, on the first of July 1690, he thought it most prudent, while the fate of the day was yet undecided, to seek for safety in flight. In a few hours he reached the castle of Dublin, where he was met by Lady Tyrconnel, a woman of spirit. "Your countrymen (the Irish), Madam," said James, as he was ascending the stairs, "can run well."—"Not quite so well as your Majesty," retorted her Ladyship ; "for I see you have won the race." [anecdote of the Old Pretender, first, as far as I can tell, in Charles Wilson's "Polyanthea," 1804]