Then-Senator Jake Garn flew on Shuttle mission STS-51-D in April 1985. He developed the worst documented case of space adaptation syndrome, for which an informal unit of space sickness was named after him:
The space sickness he experienced during the journey was so severe that a scale for space sickness was jokingly based on him, where "one Garn" is the highest possible level of sickness. Some NASA astronauts who opposed the payload specialist program, such as Mike Mullane, believed that Garn's space sickness was evidence of the inappropriateness of flying people with little training.
What is the earliest known use of this unit?
(No need for official sources; personal recollection of those involved in the Shuttle program is fine.)