ACHAÏUS, son of Ethwin, was raised to the crown of Scotland after the death of Solatius, A. D. 788. The emperor Charlemagne sent an embassy to desire an alliance with him against the English, whose pirates so infested the seas, that the merchants could not carry on their trade. This alliance was concluded in France upon conditions so advantageous to the Scots, that Achæius, to perpetuate the memory of it, added to the arms of Scotland a double field fowled with lilies. He died in 819.