Fun fact: Abbott sells methylphenidate chlorohydrate with a retardant effect so that it lasts for approximately 16 hours instead of 4, and they called it Aradix Retard lmao. I know why they called it that but I can't help but laugh every time I see it.
Not your fault of course but it was always a stupid name. It isn't arrested or inhibited, during a stage of development, resulting in an underdeveloped outcome (retarded). Like a fire retardant door stops the fire developing, as it would usually on doors. In the case of this drug, the release is inhibited, as its, presumably, a pro-drug.
They could have called it "long lasting", "pro-drug", "pro", "inhib" or "slow release" and these would have all been accurate descriptions. However, retarded isn't accurate. They chose it anyway though.