These are historical forms of Germanic languages and would be useful for etymologies.
odt (Old Dutch)
* Wikidata item: https://www.wikidata.org/wiki/Q443089
* Existing lexemes: https://www.wikidata.org/wiki/Special:WhatLinksHere/Q443089?namespace=146
* ISO 639-3: https://iso639-3.sil.org/code/odt
* BCP 47: https://r12a.github.io/app-subtags/index?check=odt
dum (Middle Dutch)
* Wikidata item: https://www.wikidata.org/wiki/Q178806
* Existing lexemes: https://www.wikidata.org/wiki/Special:WhatLinksHere/Q178806?namespace=146
* ISO 639-3: https://iso639-3.sil.org/code/dum
* BCP 47: https://r12a.github.io/app-subtags/index?check=dum
ofs (Old Frisian)
* Wikidata item: https://www.wikidata.org/wiki/Q35133
* Existing lexemes: https://www.wikidata.org/wiki/Special:WhatLinksHere/Q35133?namespace=146
* ISO 639-3: https://iso639-3.sil.org/code/ofs
* BCP 47: https://r12a.github.io/app-subtags/index?check=ofs
osx (Old Saxon)
* Wikidata item: https://www.wikidata.org/wiki/Q35219
* Existing lexemes: https://www.wikidata.org/wiki/Special:WhatLinksHere/Q35219?namespace=146
* ISO 639-3: https://iso639-3.sil.org/code/osx
* BCP 47: https://r12a.github.io/app-subtags/index?check=osx
frk (Frankish)
* Wikidata item: https://www.wikidata.org/wiki/Q10860505
* Existing lexemes: https://www.wikidata.org/wiki/Special:WhatLinksHere/Q10860505?namespace=146
* ISO 639-3: https://iso639-3.sil.org/code/frk
* BCP 47: https://r12a.github.io/app-subtags/index?check=frk