I used to believe that the term "401(k)" reffered to how much money was in the account - $401,000. This belief was further strengthened when I saw an article talking about "how to stop your 401(k) from turning into a 200.5(k)."
A childhood belief about money

others believed things like this
- I used to be really confused about the whereabouts of God.
On account of: "Our Father who Aren't in Heaven".— Tania Bradshaw - When I was a little kid I used to believe that tissue paper was money and that you could have a box of money.Anon
- I used to belive that if you went up to an ATM it would just give you money out that is not your own money.Anon
- I thought if 3 cards stopped at a 3-way stop sign then they had to stop forever until Christmas.Anon
- When I was young, I used to belive that
if you pushed the stop button in the bus it would stop for good.— Tom (Norway) - I used to believe that the term "being mugged" meant someone beat someone else with a coffee mug.— Matt Thiel