Belgium· medium· informal
ne pas avoir toutes ses frites dans le même sachet
“to not have all one's chips in the same bag”
Meaning
to not be quite right in the head
Explanation
A cheerful Belgian way of saying someone's a bit scatty or not firing on all cylinders.
Example
Il a repeint sa cuisine en violet à minuit, je crois qu'il n'a pas toutes ses frites dans le même sachet.
He repainted his kitchen purple at midnight. I don't think he's quite all there.
Origin
Belgians take their chips seriously, so comparing a scrambled mind to chips split across separate bags fits right in. Le Robert added the phrase to the Petit Robert in 2020.
Source