Office Desks Why Is The Side Piece Called A quotreturnquot

Take your average office desk.There 's the labor share, normal height WHERE your knees go under.

Then you turn to The Left or right, and it has lot desks There's a small, lower desk, Almost like a table with storage.It 's Called a "return".

Why is it Called a "return"? (I Could Almost accept it Being Called a 'turn desk' but not a 'return')