Push dagger

A push dagger (alternately known as a punch dagger, punch knife, push knife or, less often, a push dirk) is a short-bladed dagger with a "T"-shaped handle, designed to be grasped and held in a closed-fist hand, so that the blade protrudes from the front of the fist; either between the index and middle fingers, or between the two central fingers, when the grip and blade are symmetrical.

It originated as a close-combat weapon for civilians in the early 19th century, and also saw some use in the trench warfare of World War I.