Where does “ignoreth” come from?

ignoreth (English) comes from English ignore, from French ignorer, from Latin ignōrō, from Proto-Indo-European ǵneh₃- — to know.

ignoreth (English): Third-person singular simple present indicative...

Definitions

ignoreth traces back through two separate lines of ancestry.

Step	Language	Word	Meaning
1	English	ignore	To deliberately not listen or pay attention to;...
2	French	ignorer	to ignore; to be unaware of, to be ignorant of
3	Latin	ignōrō	to not know; to be unacquainted with; to be ignorant of
4	Proto-Indo-European	ǵneh₃-	to know

Step	Language	Word	Meaning
1	English	eth	A letter introduced into Old English to...