Hmm - no one has any idea about these two words?

I agree with Wolfgang... but maybe 'to pierce, press tap down'?

(English) Manual concerning datograf-Bierzapfer; Datograf Apparatebau, 74016 Heilbronn/Germany

This is the English description of the datograf-Bierzapfer:

1. Screw plastic tapping rod onto pin underneath tap. Put tapping rod onto the inner part of the can seal, for piercing press tap down with both hands, as shown in picture 1.
2. Hang tap with front part of clamp into can lid and lock by pressing down on the rear part of the tap. Loosening: Pull up snap-end of clamp.
3. Press red handle to start filling glasses.
4. Activate pump to increase pressure and beer flow. Store partly emptied kegs cool and well pressurized.

Important:
After the keg is empty, remove tap and rinse well with water, thereby pressing red handle.