Equestria girls' races and meanings and origins of their names · 6:51am Jul 11th, 2022
Sunset has already been covered in the story proper, so skipping her.
AJ is mostly Irish American, but as she's American, there's rarely a 100%. AJ is also part Native American somewhere back on her paternal grandfather's side. Her last name has already been covered in the story proper.
RD is a British Isles mix and French on her mom's side and a English, Greek, and Mexican on her dad's side. Her paternal surname is an odd way of referring to a horse shoe smith, and I don't know how someone would end up with 'Whistles' as a surname.
Twilight is Indian. Her last name is the English translation of 'Chamak' (according to Google translate). Translating one's surname was a common practice back when people anglicized their names.
Pinkie is German on her dad's side and South African on her mom's side. Her last name is the English translation of 'Kuchen' (according to Google translate). Despite being in the USA for many generations before, Pinkie's family only changed their name post WW2 because none of them could get a job because of it. This was a common problem for anyone with a German sounding name.
Fluttershy is German on her dad's side and Hawaiian and Asian mix on her mom's side. Forst was a name given to people that lived around the Black Forest in Germany. This is fitting as one of the Everfree's nicknames in 'the black forest' due to how dark it gets in places.
Rarity is Scottish and English on her dad's side and Russian on her mom's side. Alba has three meanings. It's a Latin name meaning 'white', (according to Google translate) it's the Spanish word for 'sunrise', and it's the Scottish word for Scotland. One of Rarity's ancestors moved from Scotland to England and became known as the people from Alba.