You can use git reflog show --no-abbrev <branch name>. It will output all changes made to the branch, including it’s creation, for example (I created branch xxx from master branch):
bdbf21b087de5aa2e78a7d793e035d8bd9ec9629 xxx@{0}: branch: Created from master
Note that this is not very reliable as reflog records can expire (90 days by default), and it seems like there is no 100% reliable way to do this.