It seems that 'Beurla' was once simply a word for 'language'., hence 'Beurla Ghallta' - Lowland Scots. Maybe it is related to 'beul' - mouth.
I read somewhere once that it comes from the old Irish word for gibberish. I'm not sure if that's true though.
There is a long and interesting thread on the same topic in the Irish forum here: https://forum.duolingo.com/comment/4279622/Béarla
Where does this abjective come from?
Is the B silent in pronounciation as implied in the question?
It's not silent, it's just that there's a bit of a y sound after the b. Like you'd have in Bjorn