[lmm]

The idea that debt has a specific and clearly-understood principal, term, and interest rate is a very narrow corporate-finance perspective. Many forms of debt in many cultures do not work like that (consider the notion of a "life debt"); you have a fuzzy sense that so-and-so owes so-and-so, but no specifics about exactly what or how it would take to repay that.

Technical debt is not corporate debt but it is debt. The metaphor succeeds mostly because it's accurate.