The state, quality, or condition of being an alderman, or the collective body of aldermen; aldermanic character or status.
From alderman + -ity (suffix forming abstract nouns from adjectives), created to express the abstract essence of aldermanic status and authority.
Words ending in -ity often describe what philosophers call the 'essence' of something—'aldermanity' tried to capture the special character of being part of the merchant-governed elite.
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