Definitions for eighthly
Random House Webster's College Dictionary
next after the seventh.
being one of eight equal parts.
(n.)an eighth part, esp. of one (?).
the eighth member of a series.
(adv.)in the eighth place; eighthly.
Origin of eighth:
bef. 1000; ME eightethe, OE eahtotha. See eight , -th2
In the eighth place; eighth in a row.
as the eighth in order