Today, that planet is still known by the name Venetia suggested and the Royal Astronomical Society accepted—Pluto. And, as 87-year-old Venetia reminds us today, the name is from Greek mythology, not Disney.
I came across this article yesterday while searching the Web for Pluto-related articles for my son, who I would swear said he was doing a planet report on Pluto. But it turns out he didn't say "Pluto." He has to do a report on Venus, and "Venus" is what he said yesterday.
Back to the drawing board...