prendre la poudre d'escampette

To flee suddenly without saying goodbye

Means to make a quick, discreet escape, i.e. to do a runner. The 'poudre' may evoke the dust kicked up by fleeing feet, or gunpowder; 'escampette' survives only in this expression.

Dès que l'addition est arrivée, il a pris la poudre d'escampette.

The moment the bill arrived, he did a runner.

'Escampette' is a diminutive of the old verb 'escamper' (to flee), itself from Italian 'scampare' and ultimately Latin 'excampare', meaning to leave the field. The full phrase dates to the 17th century, when it first appeared alongside the related term 'escamper', which later fell out of use.