This is a trivial question but I've always been curious about it and thought maybe there's some historians of language here. For any movie or television show I can think of that represents and "older" era, the dialogue is always the same -
"Mother, will Father be home soon?"
"Father's home! Father! What did you bring us, Father?"
"You're not supposed to be out this late by yourself, I'm telling Mother."
If those same lines came from a modern movie, of course, that'd be all variants of "Dad" and "Mom". I'm curious if there's an obvious point where the transition began? 1950s? 20s? Can we point to a movie (or a press release or written interview or something) that shows early use of those words?
Clarifying comment, since somebody asked:
I'm assuming that words like that have existed in most languages for a very very long time. After all, nobody says their newborn's first words were "Father."
For whatever reason, we seem to think that people of previous generations spoke more formally to each other. Maybe that's not even true, maybe we made it up.
So I guess that's the essence of my question, what proof do we have about the common usage / popularity in media of how children and parents spoke to each other, and how has it evolved?