'Markgraf' means border count, that is a count that was given authority in the border regions of Frankish lands, in present day Slovenia and Austria. These regions were called border counties (in Slovenian krajina, marka (both singular)). Title Markgraf (and Graf) was introduced in the Frankish region of these lands and has been in use up until 14C, I think (should go consult some books for that information).
I have never encountered 'Schenk'.
Hello, too, - in case the comparison may be helpful, think of the the English equivalent for "Markgraf" as being "Lord of The Marches" - the "Marches" being defined as the Border areas between medieval English territory, and adjoining Polities - i.e. France and Aquitaine; Wales and England, and Scotland and England.
"Schenk" is a new Title for me, too - and though I noticed it in my copy of the Manesse Codex, I haven't researched it yet.
Yours In Service to The Light, and our Dream,
dwelling in "old" Jersey
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