The term is the industry standard for subtitles that only appear when a character speaks a language different from the main audio track.
Streaming platforms sometimes default to subtitles that only translate the English dialogue for hard-of-hearing viewers (e.g., “[sighs]” or “[sword clangs]”). Meanwhile, the non-English (or “foreign language”) parts—like Daenerys’ commands in High Valyrian or the conversations between slavers in Astapor—remain . game of thrones season 3 subtitles for non english parts
In Season 3, the Old Tongue appears briefly (e.g., Tormund Giantsbane uses a phrase or two). A quality non-English subtitle file will tag these as [Speaking Old Tongue] . The term is the industry standard for subtitles