Well, I’m not even going to try being original with my origin story… it’s King Kong 1976. I was around 6 or 7 when it randomly aired on TV, and it unlocked my desire for tiny girls.
A vivid memory from the day right after : the neighbor (girl, my age) and I talked about seeing the movie, and somehow we decided to recreate the scene where King Kong blows air on Dwan. I climbed a tree in front of her house, about 10 feet up. Sitting on a branch, I closed one eye and put my palm in front of me, looking down at her on the ground and pretending to be “holding” her in my palm. She played along, acting the part, and while of course this was purely innocent, my young mind was blown and I still remember that childhood moment. 
Also in Quebec we had access to a lot of weird French and Japanese cartoons that featured shrinking, I always hoped for episodes w/ shrinking girls. It was a common trope for 80s/90s cartoons.
