Callowmeant a bird whose feathers were still growing and was untested on the wing. Fed-up referred to a falcon which had been given a full-ration of food. At which point the bird would lose interest in hunting or doing anything. Haggard meant a bird that was older and captured in mature plumage.
If you are lucky enough to live in a Mews, you are living in a building in which falconers kept their birds of prey during the moulting period, which could house several hundred birds, because mews comes from the French muer meaning to moult. Other terms, including hoodwink, lure, under the thumb, cadging, gorge, old codger and evenmantelpiece all have their origins in medieval falconry.
That falconry terms have come to be so much part of our language, is a measure of how important it was in medieval times. An afternoon’s entertainment for young girls was to bet on whose merlin could catch the most larks, and the greatest spectacular in medieval times was thought to be the Haut Vol ‘the great flight’, when the quarry bird such as a kite, raven, crane or heron climbed high into the air and the bird of prey tried to attack it from above, resulting in a great aerial battles of life and death.
Nearly everyone in the Middle Ages, rich or poor, would have kept a bird of prey, both for entertainment and for hunting for meat. If you’d gone shopping back then, you wouldn’t have seen people taking their dogs for a walk in the towns, but their falcons or hawks instead. This was because birds of prey were often caught from the wild and released again at the end of the season, so every year, women and men would have been seen walking around the towns with birds on their arms to man or tame them. It was even recommended that women took their birds to church. Can you imagine the noise and mess that created, but I bet they didn’t have trouble with pigeons in the church towers in those days.
Each falcon bore on its leg a tiny silver tablet giving its owner’s mark, and a man known as the ‘guardian of the lost’ would set up his tent on a rise with a banner flying above it so that in the vast camp he could easily be seen. Any owner seeking a lost bird would go to him, and any man finding a lost falcon would take it to the guardian. An early example of a lost property office!
Some people think that the famous Boke of St Albans which lists the birds for each social rank – Eagle for an Emperor… A Merlyon for a lady– was a record of who was permitted to keep each type of falcon. In fact a number of the birds listed were never used in falconry, so it would appear that was written more as a satire comparing the temperaments, symbolism and characteristics of birds of prey to the different classes of people.

(Old Codger? - that's a corruption of cadge, the wooden frame on which the falcons perched and which was carried out into the field by a cadger, usually an old man. The cadger used to beg tips from the nobles as payment for this service.)