Bríd pronounces the gh in
Aonghus (another name I had seen but never heard pronounced):
http://forvo.com/word/aonghus/#gaI certainly wouldn't like to have the name if the gh were silent. So from that I would assume a straight g sound for
Fearghus as well.
But then I've heard gh in
Fearghal pronounced and not pronounced (e.g., Farrell O'Gara):
http://forvo.com/search/Fearghal/So I don't know.
Some names, like
Siobhán, are pronounced differently in different dialects. In Munster (and more widely)
Siobhán is pronounced as if it were spelled
Sibheán. In Conamara,
Siobhán is traditionally pronounced as if it were spelled
Siúán - and some people have adopted that spelling to avoid having the pronunciation messed up by outsiders.
Now, not to throw
another spanner in the works, but I have heard that the traditional vocative form of
Aonghus was
a Aonghusa.
What is the probability that the traditional vocative for
Fearghus was also
a Fearghusa?
Perhaps Cian could fill us in?