assignor

transitive verb | \ ə-ˈsīn \ | as·sign

1. : to transfer (property or rights) to another the general practice by inventors of assigning patent rights —J. K. Owens

2. : to appoint to a post or duty assigned to represent the defendant

3. : to fix or specify in relationship or correspondence a party may assign as error…a failure to give an instruction, if that party properly requested it —Federal Rules of Civil Procedure Rule 51

noun

1. : assignee