Well:
- Reimu / Sanae: Ye very, very, good ol' Japanese.
- Marisa: Italian (since her name sounds like an Italian name), and her color somewhat reminds me of pasta (yellow / black color can be found in some pasta, and the white somewhat reminds me of cream sauce in pasta)
- Meiling: Ye classical Chinese
- Remi: Romanian / French, depending on what you think.
- Alice: British English
- Sariel: Ecclesiastical Latin
- Yumemi: Any scientific jargon that has frequent use of Latin words in it
- Utsuho: Ukrainian (please do not be angry at me because of this)
- Byakuren: Sanskrit
- Raiko: American English (especially the variants that are used a lot in Gen Z slangs)
- Keiki: Old Japanese
- Momoyo: Swedish (also please do not be angry because of this)
Good?