Jim's nicknames ranged from sweet things that you would both know to ones every child would get called but the one that stuck around the most was little Gordon , jim knew where it came from ,Harvey, and loved to call you it even if his partner said it was copied
Harvey called you alot of things most of them matched with food he ate like calling you 'dumpling' but the ones he used mostly was ladybug or sunshine depending on how he felt
Of course he called you the nickname he was given 'penguin' in gotham it might have been a bad thing but in the four walls you both called home it was always a name Oswald called out to get you away from your room when he came home