I removed my comment and inserted an answer. At first thanks for @Billy Kerr telling how English speakers see name ROTTERJAM. I only suspected it can have something like "Rape Biscuits" where Rape means "crispy" in the local language. English language tail pulls up the English meaning of the first part, it doesn't help at all what the name inventor possibly has hoped.
About logo and label: If still possible, invent a general trading name, something high society (I write temporarily it "Van Huismeister") which sounds plausible also in front of text "Since 1778". The font must be very traditional looking and easy to read. Let that name be the biggest element. Call the product Rotterdam Jam,if it's still possible. Tell it contains only Apple, Gember and sugar. The logo can be small, Van Huismeister's Rotterdam Jam must be well visible. The logo must be well crafted like old trading house or noble logos. You can use town scene instead of swords, crowns, lions etc... But it must look like it's created by a skilled engraver. It's simply out of the possibilities of beginners and casual hobbyists. Gold as one of the colors is welcome!
If you never make anything else than jam, you can scrap "Van Huismeister" and use instead of it "Rotterdam Jam".