The word ṛṇa is irregularly formed in the sense of 'debt.,
It is derived from ऋ, the त is changed to न ॥ The word अधमर्ण is compounded from अधम ऋणे \he who in a debt transaction holds a lower position\ - i.e. a debtor. This nipatana shows that such irregular Locative compounds may be formed; for here the first member is not in the Locative case, but the second member. The condition of being a debtor is आधमर्ण्यम् or \indebtedness:\
If this is so, then the word उत्तमर्णः 'creditor' cannot be formed? This is no valid objection. For अधमर्ण is illustrative only of something to be paid hereafter, in consideration of something formerly received; and thus includes उत्तमर्ण also; which also has been so employed by the author himself in धातेरुत्तमर्णः (1. 4. 35).
The word ऋण we use in sentences like ऋणं ददति, ऋणं धारयति ॥
Why do we say when meaning 'debt'? Observe ऋतं वक्ष्यामि, नानृतम् ॥,