Double jump replenishers are little blue and white orbs in I Wanna Be The Boshy. They give the player an extra

A cluster of doublejump-replenishers

double jump. They appear throughout the game, and are necessary to complete it.

You can use as many as you like before touching the ground, but collecting multiple Double-jump replenishers does not grant you a stack of extra jumps. Only one extra jump can be held onto at a time.