Called himself "daddy" during sex

Mellise • ~BFP August 2016!~ 👶🏻💙 (used pre-seed.softcups.opks) Pregnant with #2 Due Jan,11,2019
Ookay, just can't get this out of my head. I've been with my boyfriend for two years and some months (So we have had a LOT) of sex.) 
Enough for last night to peak my curiosity. We were laying in bed and making out and it was very passionate and heated and Boom! we were naked, having sex (doggie) looking in our big closet mirrors when he said "yeah, make daddy cum." He trailed off very quickly right when he caught himself say it! Like it slipped by total accident. He has NEVER said anything like that before.. not even close! Lol 😳 I totally went with it didn't skip a beat or pause. And he might have thought I didn't notice. Lol but it's so weird?? Where did he get that from? He doesn't watch porn. & in two years has never referred to himself as daddy. (I remember him once saying it was weird and turn off when girls do that?) Does he want me to call him daddy ? Or was that some kind of random heat of the moment fluke...
What are your thoughts? Lol
Side note I am 14 weeks with our first, maybe something to do with it. But I could tell he said it by mistake and tried to quiet as soon as it came out of his mouth.