Different Names for Step-Dads apart from the name "Dad/Daddy" ?

Heya Sisters,
I have 3 kids and I split from their dad almost 3 years ago, it took me a little while to get back into the dating scene and then I met the most gorgeous man after I kissed a few frogs. We've been together 16 months and he's been apart of my children's lives for the last 10-11 months. We didn't involve him majorly until we had been together quite a few months. My youngest has been trying out and I say trying out because it happens a fair bit, calling my new partner Dad/Daddy etc he feels a little overwhelmed at the thought and also doesn't want to step on her actual Dads toes. He still sees her once a week. I don't want to deter her from calling this man dad in the future as he is everything a dad should be, they've formed quite a bond and she misses him terribly when he is gone. Well just say he's FIFO. She sees him two nights and 2 mornings a week. He's aware that when we have our own that she will see him being called dad by our children and that it's not really a big deal and that her actual Dad will get over it in time. How can we encourage the use of his name, or what other names do your kids call their stepdads that's different to Dad/Daddy. I want to make it easier on the both of them. My partner has taken to parenting quite well and works with me as a team. I know it's normal to want to call the main man in your life Dad as I have called my step dad plain old dad since he and my mum were together for a year. (My actual father hadn't been in the picture for years before then) I'm just trying to work out what else is out there so that the two of them can get there own special thing worked out. Ta Ladies!