Meaning a sick person, usually someone with a stomach flu. The 'Sam' would throw up often unexpectedly.
A 'Sam' is also a busybody, or an extremely annoying CPA (certified public accountant).
Person A: Oh my God, why are you being such a Sam?! Stop memorizing all my debts to the cent!
Person B: Yeah! Stop being such a SAM!
Person A is throwing up a lot.
Person B: Wow, you are being very Samish.