means A part of something that projects or juts out beyond the part below it, whether a ledge of rock, a roof's edge, or a debt that lingers past its time.

from A plain English compound, bolting together "over" (from Old English ofer, the same word that hovers above so much of our speech) and "hang" (Old English hangian, to be suspended). Together they describe exactly what they say: something hanging over. The literal sense of rock and roof came first; the figurative "overhang" of leftover stock, debt, or threat is a later borrowing of that same looming image.