Why my girlfriend always calls me daddy?

This is bit weird, but yes! My girlfriend calls me daddy. lol. She always say"Hello daddy" or something extremely weird like Cya tomorrow daddy". Holly shit why she say this? Im extremely confused and have no idea about the reason. She has started calling me daddy since last weeks. Earlier, she never called me daddy or something related.

Why she say me so?
Why my girlfriend always calls me daddy?
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