The capital letter may suggest that it is the name of something?
Otherwise, I have heard it as a verb "to blag" which means to try to fake knowledge e.g. "I blagged the test."
It's UK slang and it's been around for long enough to make it into the OED.
It's hard to say which of several possible meanings - if any - is relevant in this situation (due to absence of context).
Thank you so much! Actually, i was in a forum where there were a lot of people, maybe it is a name or maybe not. I'll try to get back in the chat and check the name out.
Alexandre
I wonder how closely "blag" is related to "blaggard"; yes, I know that the latter is equated to "blackguard" and hence encompasses a much wider variety of sins or offenses.