Well, it is taken to be a rude word or term, but not an extremely rude one... Also, although somewhat archaic, the term "Soda Jerk" was an honorable profession for a young man working at soda fountains concoting various soft drinks. The term is still used but sparingly. Additionally, it seems that rude terms nowadays are more likely to be obscene and most lighter rude terms are disappearing...
winker remains rude because you can still hear the word wink in it. [deliberate misspelling, for the obvious reason] But ******, for instance, is less rude even though it means the same thing, because - as with jerk - the origin is less obvious, I would guess.
Jerk isn't the equivelent of your English word. It's not really that bad of a word here. There are words in England that are considered bad here but not there. It's just really a difference in culture
As Clanad mentioned, a soda jerk was the fellow who worked at lunch counter or soda fountain. He jerked the handle of the dispenser toward him to make the soda come out.
Any body remember the dance from the 60s called the Jerk?
One simply thrashed with jerky twitchy body movements.
Jerk is a perfectly good word and when used without "off" has no dirty connotations in American English.