tithe
n.
a tenth part (originally of produce) due as support of the clergy, c.1200, from Old English teogoþa (Anglian), teoþa (West Saxon) "tenth," from Proto-Germanic *teguntha, from PIE *dekmto-, from *dekm "ten" (see ten). Retained in ecclesiastical sense while the form was replaced in ordinal use by tenth.
v.
Old English teoþian "to pay one-tenth," from the root of tithe, n.. As "to impose a payment of a tenth," late 14c. Related: Tithed; tithing.