The state or quality of being debonaire; suave and elegant manner or character.
From 'debonaire' plus the native English suffix '-ness' (from Old English 'ness' originally meaning a promontory or headland, later generalized to mean state or quality). This is the Germanic alternative to the Latinate '-ity'.
English speakers ended up with both '-ness' and '-ity' doing almost the same job because we inherited them from different languages—'-ness' from our Germanic roots and '-ity' from Latin—so we got redundancy but also stylistic choices.
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