This Russian expression, literally translated as ” Neither fish nor meat” is used to describe a thing/person that is rather mediocre, average, neither good nor bad, doesn’t have a clear position in life.
This expression has a very interesting etymology that dates back to the 16th century.
This is when Protestant movement started and as we know from History there were a few tensions between catholics and protestants at the time. No wonder: their view on everything were completely different, including religion itself, the ideology, norms, and also way of living.
As a matter of fact, protestants ate more meat: it was considered to be simple and modest food, and it opposed them once again to catholics who preferred fish considering it traditional lenten food.
So, people who couldn’t decide on whether to be a catholic or a protestant, were mockingly called ” Neither fish nor meat”.
Gradually the meaning evolved into indecisive, unsure, neither good nor bad, average, etc.
This expression is common to many languages.