The name Vaseline preserves a scientific idea that turned out to be wrong.
Robert A. Chesebrough sold the petroleum-based ointment under that name. Etymonline records the word as a trademark in 1872. Wikipedia points to an 1872 patent filing in which Chesebrough says he named the product Vaseline. Registration dates vary by source, and one history gives 1878 for the United States.
The name is a three-part blend. The first part is German Wasser, "water." The second is Greek elaion, "oil," the word that also gave English oil its ancestry. The third is -ine, an ending that made products sound chemical and modern. An 1877 dental journal glossed the whole thing as "water-oil."
Why water? Etymonline says the name reflects Chesebrough's belief that petroleum formed underground when heat and pressure acted on carbon in certain rocks and on hydrogen from water. That is not how petroleum is now understood to form, but the brand name kept the idea.
The product story behind the name is also partly legend. Tradition says Chesebrough visited the new oil fields at Titusville, Pennsylvania, in 1859, after Edwin Drake's drilling success. There he supposedly noticed "rod wax," a waxy residue that clogged pumping equipment. One biography page presents this as tradition, not documented fact.
What is documented is the factory. Chesebrough added Vaseline production to his Red Hook works in 1870, and the jelly was on sale by 1871.
The word has a cousin among nineteenth-century petroleum names. Abraham Gesner coined kerosene in 1852 from Greek kēros, "wax," plus -ene. Like Vaseline, it paired a Greek root with a chemical ending to make a product name that sounded like science.
None of the sources I read says when Chesebrough chose the name or exactly how. The German and Greek roots and the water theory are what the dictionary record supports.