I just watched the film The Slums of Beverly Hills. It’s set during the 1970’s. In one scene the father whistles and shouts “Jackson!” when looking for service in a restaurant. The black waiter grimaces at him and doesn’t come to the table. The man’s kids admonish him for using the term because it’s racist. What does the term mean and what are its origins?
I’m not sure that it’s inherently racist, it’s just the usage. Jackson is a relatively common surname for Black Americans, so the racism of the thing comes from the dad seeing a black man and calling him a generic “black” name. It’d be like trying to get a Hispanic waiter’s attention by yelling “Hey, Jose! Over here!”
Ah, that would make sense I suppose.
If it were set in northern NJ, I would think it could be a reference to “Jackson Whites.”
There’s really only one polite, PC way to flag a busboy, and that’s to catch their attention (maybe with an outstretched hand, as if gesturing for a taxi), and saying something like “excuse me,…”. I’d feel awkward calling to one with “busboy…” regardless of that person’s race (or gender). Arkin’s character was rude in whistling, pushing it further by shouting, and racist for shouting “Jackson!”. And as the movie shows, that was the least of his problems. 
There was a similar insult in Wes Anderson’s The Royal Tenenbaums, when Gene Hackman’s Royal T. insults his ex-wife’s African-American fiancee Henry Sherman (Danny Glover) by calling him “Coltrane”. It was so awkward, crude, and inept (when you think about it, Coltrane had a more enduring form of genius than any of the Tenebaum children), it came off as inadvertently funny, actually, and was just one in a series of incidents in which Royal Tenenbaum is rude, condescending, or un-PC.
Jackson is the perfectly-fine nickname for black band leaders in 40’s movies. “Hit it, Jackson” is heard in every one of those.
Except that Jackson Whites are white even though they supposedly have the blood of escaped slaves in them.
It suddenly appeared in about 1941 as a form of address to anyone, black or white, as long as you were calling him “buddy.” Very common in the US military. And, as others have said, a jazz context.
It probably comes from “Jack,” which was a term used quite a bit the previous 100 years when you didn’t know someone’s name.
When I lived in Jackson, MS, I oft heard references to the “Jackson Accent,” FWIW.
In the context it’s pretty offensive indeed, though maybe not racist specifically. It’s more a case of picking a name and calling somebody by it.