According to George:
“Early on, it was that Anakin had been more or less created by the midi-chlorians, and that the midi-chlorians had a very powerful relationship to the Whills [from the first draft of Star Wars], and the power of the Whills, and all that. I never really got a chance to explain the Whills part.”
https://www.starwars.com/news/star-wars-episode-i-the-phantom-menace-oral-history