Where does “Southern Mongolia” come from?

Southern Mongolia (English) comes from English Mongolia, from English Mongol, from Mongolian ᠮᠣᠩᠭᠣᠯ, from Latin -icus, from Ancient Greek -ικός, from Ancient Greek -κός, from Proto-Indo-European -ḱos — -y, -ic.

Ancestry of “Southern Mongolia”, step by step

Southern Mongolia traces back through two separate lines of ancestry.

via English Mongolia

StepLanguageWordMeaning
1EnglishMongolia
2EnglishMongolA person from Mongolia; a Mongolian; A member of...
3MongolianᠮᠣᠩᠭᠣᠯMongol, Mongolian
4Latin-icusbelonging to; derived from; of or pertaining to;...
5Ancient Greek-ικόςof or pertaining to, in the manner of; -ic
6Ancient Greek-κόςforms adjectives with the sense of 'of or...
7Proto-Indo-European-ḱos-y, -ic

via English Southern

StepLanguageWordMeaning
1EnglishSouthernfrom or pertaining to the southern part of any...
2Old Englishsūþernesouthern, southerly, coming from the south; of...
3Proto-Germanicsunþrōnijazsouthern
4Proto-Indo-Europeansóh₂wl̥sun
Every word from Proto-Indo-European -ḱos