Even before that tale got abroad, jimmies was trailing clouds of factoid and fancy. Its origins are murky, so — like “the whole nine yards” and “the real McCoy” — it attracts just-so stories, some plausible and some less so. At the “Boston English” section of the website UniversalHub, commenters will tell you that jimmies are named for the Jimmy Fund, the children’s cancer charity; for a kid named Jimmy who got them on his ice cream as a birthday treat (“they’re Jimmy’s”); for a mayor named Jim Conelson, or a Jimmy O’Connell who was extra generous with sprinkles; and for a guy who (maybe) ran the chocolate-sprinkles machine at the Just Born candy factory.
Of all these theories, only the last is even remotely plausible. Just Born, the candy company that still provides us with our marshmallow Peeps and Mike and Ikes, was founded in Brooklyn in 1923, according to its official history, though patriarch Sam Born had already come up with candy innovations like a machine to put sticks into lollipops.
The company’s website claims that “jimmies, the chocolate grains sprinkled on ice cream, were invented at Just Born, and named after the employee who made them.” (Company spokesmen have mentioned a Jimmy Bartholomew, but his existence is unverified.) But company histories often include a fudge factor, and this claim of invention seems dubious: Chocolate sprinkles, so called, were already popular in the 1920s, the newspaper archives show. The Nashua, N.H., Telegraph is advertising a treat made with chocolate sprinkles in 1921, before Just Born was born.
Rest of the story: http://www.boston.com/bostonglobe/ideas/articles/2011/03/13/the_jimmies_story/