It is not often that I (lexicomane that I am) run across an English word with which I am entirely unfamiliar, but I have just encountered “hirsel” for the first time. It is primarily a Scottish and northern word meaning ‘the entire stock of sheep on a farm or under the charge of a shepherd’; it is related to “herd” (though borrowed from Old Norse hirzla, from hirtha ‘to herd, tend’), which is a help in remembering its meaning. I found it in the following passage (from an interesting article, “The Ecology of Medieval English Monasteries” by Austin Mardon of Greenwich University):
Several of the herds that roam the Yorkshire dales today have existed continuously since the 13th century. It is worth noting that it is illegal to sell off a complete hirsel from any mountain because it takes several generations of sheep to learn their individual “sheep-walk” and some of the older, experienced sheep must be left to guide the young, who would otherwise starve.
I hope the law is still on the books; I like it a great deal.