I don't know why, but I went into this thinking it was going to be about soda jerks.

Had to go to the comments in the linked post to find the reference to the soda jerk. And "jerking" was apparently pulling on the (seltzer) tap.

I suppose if "soda jerk" was thought to be a menial job (reminded of one of the threads in the film, "The Best Years of Our Lives" (1946)) ... then the original meaning of "jerk" as a loser might have come from that.

I went into this thinking it was going to be about culinary spices. But I had just finished watching a video on jerk chicken so my mind was already in the wrong place…