I was disappointed that the article, despite it's title, never actually tells us how these group names came about. From some reading a while back, it seems that many started to be used after the 1968 book, An Exaltation of Larks, became popular. It was written by the Inside the Actors Studio host James Lipton, and includes some terms he made up himself, as far as I can tell (the back cover states " In it you will find more than 1,100 resurrected or newly minted contributions...").
In the article it is shown that many of them were already present in one of the first printed books, in 1486: "The Book of Hawking, Hunting, and Blasing of Arms".
To go further back in time would be possible only for words that would happen to be mentioned in some ancient manuscripts, which is not very likely for words designating flocks of birds.
Oddly enough, the Anglo-Saxon chronicles, which are among the few sources of news of events in the 600-1000 period, spends considerable ink on describing unusual actions of flocks of birds. That and ecclesiastical events. You do get the occasional account of wars, kings, land deeds, etc. but the frequent mention of birds is odd. Perhaps they were seen as portentous?
