My toddler has been calling my boyfriend "daddy"

My son's biological father is not in his life at all, no interest (wasn't even there for the latter half of the pregnancy). I don't say the word Daddy or dad or anything like that around my son. I started dating a wonderful person back in September who loves my son to pieces and wants to eventually adopt him (years down the line), positive scenarios permitting. We don't do anything to put words in my son's mouth, neither of us. My family doesn't either. But my almost two year old has starting calling him daddy and looking for him when he isn't here (he isn't distraught, just confused and calls for him). My son has more than enough love and I don't think that he's lacking any attention, he just really enjoys the company of my boyfriend.

It's just weird that he picked that term to call him by 😂 my son watches baby videos and traditional "Mom, Dad, kids" families are portrayed but we are very open and honest about all family types. I have been a single parent to him and that is all he knows, so it's just odd lol. It's like he is cementing the glue of my future. I'm not upset at all, my boyfriend is a fucking saint and treats me so well. He always includes my son for things and when my son started calling him daddy, he just about cried (we were in public). So it's not a bad thing at all, I'm just astounded by the natural progression of things. I only ever refer to my boyfriend by his name so it feels like this all came out of left field and we both feel super mooshy about it.