"...Tomorrow is St. Valentine's Day, when every bird chooses her mate; but you will not see the linnet pair with the sparrow hawk, nor the Robin Redbreast with the kite. My father was an honest burgher of Perth, and could use his needle as well as I can. Did there come war to the gates of our fair burgh, down went needles, thread, and shamoy leather, and out came the good head piece and target from the dark nook, and the long lance from above the chimney. Show me a day that either he or I was absent when the provost made his musters! Thus we have led our lives, my girl, working to win our bread, and fighting to defend it. I will have no son in law that thinks himself better than me; and for these lords and knights, I trust thou wilt always remember thou art too low to be their lawful love, and too high to be their unlawful loon. And now lay by thy work, lass, for it is holytide eve, and it becomes us to go to the evening service, and pray that Heaven may send thee a good Valentine tomorrow."
The above is from "The Fair Maid of Perth, or St. Valentine's Day".
Named after the Bishop of Terni, who was martyred in the 3rd century, Valentine's Day became associated with romantic love, and the selection of partners, through to the influence of such authors as Chaucer.