Server at a
soda fountain or
ice cream shop. The name derives not from the attitude of
teenage staff who might work there, but is a short form of soda
jerker, simply an explanation of the job. In the
19th century, dispensing
carbonated water required back-and-forth jerking motion on the
dispenser levers to control the
spray.
Short-order code probably originated with soda jerks, not short-order cooks, according to Harold W. Bentley's 1935 article "Linguistic Concoctions of the Soda Jerker" in American Speech.