An exclamation "By George"

By George! is an exclamation of determination, it is antiquated now but you can see/hear it's usage in movies from the 30s and 40s where elderly people sometimes say it. It's always used in the "I'll do it, I'll get it done, I will." sense. By golly has similar antiquated usage. Without doing any research, I suspect its etymology has some relation to the Kings George of England. Edit: Etymology. "By (God and Saint) George" is an old English oath invoked immediately before charging into battle as late as World War I. A version of the oath can be found in Shakespeare's Henry VI (part I), written circa 1589 and set in 1431. https://en.wiktionary.org/wiki/by_George