How did 12 become the default number of jurors (at least in the US)?

I was listening to a true crime podcast recently (the best possible source of legal knowledge) and the hosts ended up talking about a murder trial with 8 jurors. It got me wondering how did 12 become the default number of people to have in a jury (at least in the US)? If I remember my undergrad Constitutional Law class the right to a trial by jury is guaranteed by the number of jurors isn't set.

Is 12 actually the default number of people for a jury or does that come from pop culture as opposed to actual legal practice?

Why 12? Why not 8 people comprising a jury regularly?