swap 
(swŏp)
(swŏp)v. swapped, swap·ping, swaps
v.intr.
To trade one thing for another.
v.tr.
To exchange (one thing) for another.
n.
1. An exchange of one thing for another.
2. A contract in which two parties agree to exchange periodic interest payments, especially when one payment is at a fixed rate and the other varies according to the performance of a reference rate, such as the prime rate.
[Middle English swappen, to strike, strike the hands together in closing a bargain.]
swapper n.