Where does “Marketenderin” come from?

Marketenderin (German) comes from German -īn, from Middle High German -īn.

Ancestry of “Marketenderin”, step by step

Step	Language	Word	Meaning
1	German	-īn	creates the female form for many nouns for living beings; umlaut usually occurs in monosyllables, but rarely in polysyllables
2	Middle High German	-īn	—