Having worked in a kitchen, "knife behind" if you have a knife or just really want to make sure nobody moves, "behind" if you are more okay accidentally bumping booty.
In German they have “Wahrschau” which coincidentally also sounds like the name of the capital in Poland, however it comes from shipping industry and to my knowledge is a shorter version of “Wahr nehmen und schauen” which roughly translates to “hey, look at me”. I might be wrong, but that’s what I’ve heard.
Sorry about the typo. My German is a rusty 😅
As to whether it’s a shipping or a northern thing, could be both. I used to study maritime navigation in northern Germany and this was a very common saying in between the maritime crowd. Did hear it out side of it though. But I might be mistaken.