Blag is word with multiple meaning. Fyee, ayyee, swaagg fuck. You just substitute the real word with blag
Oh, she Down to Blag (Fuck)
Where the Blag you been (Fuck)
Dude, I just got my license, blaaggg (swaaaag)
Dude, that guy is blagged up! (Swagged)
Blag me the fuck out (Swag)
Comes from the old word "blackguard", a contemptible and untrustworthy person, which was pronounced "blaggard".
The sound of the last part "ard" became confused with the suffix "ard": meaning a person who does an action, as in drunkard. "Blag" becoming the contemptible untrustworthy action.
I first came across it as a teenager working on a building site nearly 50years ago, when an old Irishman accused another of "fucking blaggarding". I didn't know what it meant, but was obviously a bad thing to accuse someone of and not done lightly. These days it seems to have lost its former vehemence and is used more in the manner of petty criminals boasting of their offences.
"Where did you get that from?"
"Ha ha ha, fucking blagged it didn't I.
"Did your wife say anything about the time you got home?"
"Yes, I gave her some blag about working late."