Arrear
ARRE'AR, adverb [Latin ad and retro.]
Behind; at the hinder part. In this sense obsolete. But from this use, we retain the word as a noun in the phrase, in arrear to signify behind in payment.
ARRE'AR, noun That which is behind in payment, or which remains unpaid, though due. It is generally used in the plural, as the arrears of rent, wages and taxes; and supposes a part of the money already paid.