tithable

Word History: A tithe is a tenth, etymologically speaking; in fact, tithe is the old ordinal numeral in English. Sound changes in the prehistory of English are responsible for its looking so different from the word ten. Tithe goes back to a prehistoric West Germanic form *tehuntha-, formed from the cardinal numeral *tehun, "ten," and the same ordinal suffix that survives in Modern English as -th. The n disappeared before the th in the West Germanic dialect area that gave rise to English, and eventually yielded the Old English form tēothe, "tenth," still not too different from the cardinal numeral tīen. But over time, as the former became tithe and the latter ten, and as tithe developed the specialized meaning "a tenth part paid as a tax," it grew harder to perceive a relationship between the two. The result was that speakers of English created a new word for the ordinal, tenth, built with the cardinal numeral ten on the pattern of the other regularly formed ordinal numerals like sixth or seventh.