This is a second person past tense form of "to owe." To give a parse of the morphology:
owe - d - st
owe - past - 2sg
The "-d" or "-ed" is the usual past tense (and participle) marking we know and love today. The "-st" is the second person singular agreement morpheme, which we no longer have in Modern English.
As for its meaning, "owed" sort of makes sense, but this might be a more archaic use for it.
Edit: Here is the advanced search page for Open Search Shakespeare:
If you select Regular Expression and search
.*edst, you'll find a lot more examples with more easily recognizable verbs.