"Pounded like a rented
gerbil" is a phrase used to describe disastrous events- usually painful financial setbacks.
As you can
imagine, rented gerbils would be the unfortunate recipients of an especially rough and vigorous pounding experience, when compared with the more tender romantic encounters of privately owned gerbils. After all, you'll be returning the poor rodent right back to the rental
office tomorrow, so why bother taking good care of it?
How'd it
go for me at the blackjack tables last night? I got pounded like a rented
gerbil, that's how! I dropped almost two grand! Fuck... that'll teach me to gamble with
money I can't afford to lose.