debt
late 13c., dette, from O.Fr. dete, from L. debitum "thing owed," neut. pp. of debere "to owe," originally, "keep something away from someone," from de- "away" (see de-) + habere "to have" (see habit). Restored spelling after c.1400.
owe (v.)
O.E. agan (past tense ahte) "
to have, own," from P.Gmc. *aiganan "
to possess" (cf. O.Fris. aga, O.N. eiga, O.H.G. eigan, Goth. aigan "to possess, have"), from PIE *aik- "to be master of, possess" (cf. Skt. ise "he owns," isah "owner, lord, ruler;" Avestan is- "riches," isvan- "well-off, rich").
Sense of "to have to repay" began in late Old English with the phrase agan to geldanne lit. "
to own to yield," which was used to translate L. debere (earlier in Old English this would have been sceal "shall"); by late 12c. the phrase had been shortened to simply agan, and own (v.) took over this word's original sense.
An original Germanic preterite-present verb (cf. can, dare, may, etc.). New past tense form owed arose 15c. to replace oughte, which developed into ought (1).