the marauders all love to call James names that annoy him; Sirius calls him Jimmy or Jame (singular) Peter calls him Jameson (James has repeatedly told him that’s not his full name) and Remus calls him Séamus (he claims James needs a ‘good Irish name’)

In the version of reality where Jily happens only after a long hex-ridden courtship and numerous rebuffs on Lily's part, I submit that during those pre-Jily years Lily is the only one who calls James by his actual name. And he hates it. He's annoyed when the Marauders call him anything other than James but he desperately wishes Lily would call him anything other than it. He knows an affection pet name is too much to ask for, but he'd settle for a nickname. Even a silly one. Fuck, he'd even take a mean nickname if it came from Lily Evans.