Grand question

How did the word grand become associated with $1000.00?

Send me a grand and I’ll tell you.

Also, “large” = $100 bills, at least at the bank. I do not know why. I was in the bank the other day withdrawing some money and the teller (why aren’t they just called cashiers or something like that) asked me if I wanted the money in “large”. First, I didn’t know “large” was a noun. Second, I thought she said “go large” and wondered if I was in the local fast-food retaurant by mistake!

A Grand was originally a piano.
This was originally converable into 100 Gold Eagles, or $1,000.