smuggycfa

Ill take a shot at the short payer swaption:

This would also be a receiver swaption.

A payer swaption allows you to pay fix receive float, a receiver swaption allows you to pay float receive fixed.

A firm may do this if they are already receiving a floating rate through a lending program and would like to convert it to fixed; much in the same way that a firm who borrows float enters a plain vanilla in order to pay fixed.