What do you think B.F. Sword stands for?

Big F***ing Sword obviously

it's an homage to the BFG, so take your conclusions

Best Friend's Sword. He always has better things than you so you borrow his stuff.

i always thought it was best f*cking sword

Big Fucking Sword

Best Friend Sword :P

Baron's Fabulous Sword. Because isn't enough.

Bombacious Fabulous Sword.

I thought it was just like Big Fat Sword

This should help you figure it out:

https://en.wikipedia.org/wiki/BFG_(weapon)