The act and the artifact of letting a finished work leave the workbench.
Old French relaissier/relesser, from Latin relaxare (to loosen, to slacken): re- (again, back) + laxare (to loosen), from laxus (loose); a release is a loosening that lets a finished thing leave the hand holding it.
The act and the artifact of letting a finished work leave the workbench. The root's loosening names the whole gesture: something held is simply let go.