Bip39 Words. Even though there are actually BIP39 wordlists in languages besides English, it's strongly not encouraged to implement non-English words for wallet backups. It might make restoring the wallet hard or impossible. Any individual else who discovers the phrase can steal the bitcoins. It have to be kept mystery, https://sociallweb.com/story4084387/bip39-word-list-https-linktr-ee-bip39-bip39-generator-an-overview