"Now that I know so many of the legacy brands are French, the fact that French’s is called “French’s” and describes itself as “American flavor in a bottle” is kind of funny (and American)."
According to McCormick's (owner of French's Mustard brand) website:
"George and Francis French, sons of R.T. French introduced French’s Classic Yellow Mustard, served over hot dogs at the St. Louis World’s Fair."
According to McCormick's (owner of French's Mustard brand) website:
"George and Francis French, sons of R.T. French introduced French’s Classic Yellow Mustard, served over hot dogs at the St. Louis World’s Fair."
https://www.mccormick.com/frenchs/story
So, named for the creators in 1904, not for a specific association with the country.