Don't peep at bamboo joints
This saying is likely a mistaken rendering of a proverb that says not to peep on both sides of a bamboo joint. " タケフの両ノゾキするべからず " 両ノゾキ means double peep (See diagram).
The black structure is a bamboo joint. peeps at it. A peep threatens to cut something, but a bamboo joint cannot be cut with the next move. Thus, peeping at a bamboo joint is a wasted move — but remember: The bamboo joint may be short of liberties.
Here, throws itself against a wall. This is worse, because it loses a liberty immediately, but the idea is more or less the same: a bamboo joint is almost as strongly connected.
The proverb in fact warns against moves that are not peeps at bamboos as such, but will inevitably become if you read a little further. In particular peeping at both sides of the bamboo must be avoided. Here is a nice illustration of this proverb:
White here is called a trick play in a Korean book. That seems unfair. But the point is that Black might play at a in answer. Then after to , Black would be peeping at both sides of a bamboo joint, which is taboo. One peep may be acceptable, but with stones at and a it can't be that both are efficient.