Liz, it's plural, a group of hunchbacks. As I wrote, since they are "tall hunchbacks"; I think they are probably not real hunchbacks but people who are imagined as hunched over when they are either staring at or hanging over Máiri Dhubh. Be sure to see the other thread for more information.

I know how to contact one of the Kennedy family re their recording, hopefully to get an answer to Rory's query about the recording, and to resolve my own difficulties translating one line of the chorus. I may leave it to Linn P, whom Liz asked personally about helping us learn this song, to do that communication as well as to chose which verses from the different publications to make "our own". So I expect to get back to the thread with some answers, hopefully within a few weeks.

The modern spelling of "Bithidh" (will be) is "Bidh". Either is acceptable.
Beurla, the English language, starts with a B, not an h. The letter "h" is just above "b" on the keyboard, so it's an easy typo to make.