What is the meaning of Pumpen?

definite singular of pumpe

to pump (use a pump, work like a pump)

to pant, to breathe intensely due to exertion, to exert or push oneself

to pump, weightlift, work out

to borrow or lend; sometimes used in finance contexts, then usually implying unsustainable business models

definite masculine singular of pumpe

Source: wiktionary.org