Where does “उपस्थ” come from?

उपस्थ (Sanskrit) comes from Sanskrit स्था, from Sanskrit -प्-, from Sanskrit -इत, from Proto-Indo-Iranian -tás, from Proto-Indo-European -tós — Creates verbal adjectives from verb stems.

Ancestry of “उपस्थ”, step by step

उपस्थ traces back through two separate lines of ancestry.

via Sanskrit स्था

StepLanguageWordMeaning
1Sanskritस्थाto stand, station oneself, take up a position on;...
2Sanskrit-प्-
3Sanskrit-इतforms adjectives from nouns: -ed, having, furnished with
4Proto-Indo-Iranian-tásCreates verbal adjectives from verb stems
5Proto-Indo-European-tósCreates verbal adjectives from verb stems

via Sanskrit उप

StepLanguageWordMeaning
1Sanskritउपtherefore, moreover; towards; near
2Proto-Indo-Europeanupóunder, below
3Proto-Indo-Europeanh₃ewp-
Every word from Proto-Indo-European -tósEvery word from Sanskrit -प्-Every word from Sanskrit स्था