back scratcher

or back-scratch·er, back·scratch·er

noun

a long-handled device for scratching one's own back.
a person who exchanges favors or services for mutual advantage.

Origin of back scratcher

First recorded in 1785–95

Related formsback scratching, noun

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018