I too wonder where this trope came from. Tolkien's dwarves were based on the Jews, he even admitted as much. It wasn't even an antisemitic thing; he admired the solidarity, industriousness and overcoming of hardships he had witnessed.
I find it annoying when Americans say "British accent" when they mean "English accent". Scottish, English, Welsh, Faroese and Irish accents are all "British".
It's like id I called somebody with a Mexican accent "American". It's technically correct, but insultingly broad.