PWND means “Owned”. The PWND is typically used after losing badly during an online game (e.g., I was really PWND, man.) When one player completely annihilates another, the loser is said to have been PWND (i.e., owned, beaten, defeated).
But there is also a sexual connotation I will leave to you to discover...There might even be pics.
:D
I think it had its genesis by being a typo in one of those old low-resolution heavily pixelated games. I believe it was supposed to be "owned" but was typo'd as "pwnd" (sort of like "all your base are belong to us"). I think it is pronounced so as to rhyme with "owned".
As to the "69", how is that even obscene in a world with "pride month", Cardi B and her "WAP" on live TV, drag queen story hour, Deniro yelling "F*** Trump" on live TV, commercials with women shaving their pubic area, etc?