Merriam-Webster's Collegiate® Dictionary, 11th Edition
SWAP
I. verb (swapped; swapping)
Etymology: Middle English swappen to strike; from the practice of striking hands in closing a business deal
Date: 14th century
transitive verb
1. to give in trade ; barter , exchange 2, to take turns in telling , intransitive verb to make an exchange, swapper noun
II. noun
Date: 1625
an act, instance, or process of exchanging one thing for another