Where does “eightetenthe” come from?

eightetenthe (Middle English) comes from Middle English eightetethe, from Old English eahtatēoþa, from Proto-Germanic *ahtudô tehundô.

Ancestry of “eightetenthe”, step by step

Step	Language	Word	Meaning
1	Middle English	eightetethe	—
2	Old English	eahtatēoþa	—
3	Proto-Germanic	*ahtudô tehundô	—

eightetenthe — Etymology, Origin & Word History | Etymology Explorer