Rafałku - vocative of a diminutive of Rafał (the name of yours truly in the tongue of consonant floosies), translates roughly to Oh, lil' Rafał boy. Augmentative and diminutive forms are used in Polish relatively frequently compared to many Indo-European languages. They're also more layered (for the lack of a better word), by which I mean that you can say: kotek (kitten), koteczek (lil' kitten), kiciuś, kociak (kitten, or calling someone babe), kociaczek (same but lil'), kiciunia, kociątko (lil' baby kitten).
Useless linguistic trivia (you deserve it since you arrived here through a series of notes):
Wódka (vodka) in Polish is a diminutive of an augmentative, meaning literally little big water.
woda (water) → wóda (big/heavy/potent water) → wódka (little/cute yet heavy/potent water)