Look up an ISO 639 language. Pass code in any form — 639-1 (en), 639-2/B (ger) or 639-2/T (deu) — or name (English, partial match). Returns the English name and all sibling codes (alpha-2, alpha3-B, alpha3-T), so you can normalize a messy language tag to canonical ISO identifiers and resolve the bibliographic-vs-terminological alpha-3 split (e.g. German = de / deu / ger). Bundled authoritative ISO 639 data.