“Je weet toch” was the original, classic and epic expression which was originated in Amsterdam, The Netherlands.

Meaning :

You know (what I mean, what it is, what’s up)

Other cities tried to think of something similar and took inspiriation of “je weet toch” and changed it to “je weet zelf” or “jwz” mostly used by teenagers.

Nice to know:
The popular radio station FunX used “je weet toch” in their bumper ad.