'assortedness' originates from English, formed from the adjective 'assorted' plus the noun-forming suffix '-ness' (Old English in origin), where 'assorted' itself comes ultimately from Old French 'assortir' (to arrange/fit together).

'assorted' came into Middle English via Old French 'assortir' (from a- + 'sortir'/'sorte' related to Latin 'sors, sortis' meaning 'lot' or 'kind'), then the abstract noun-forming suffix '-ness' (Old English '-nes(s)') was added to produce 'assortedness' in Modern English.

Initially related to the idea of things being arranged or matched ('arranged together' or 'fitting together'), the sense shifted to emphasize the presence of different kinds together — the current meaning 'the state or quality of being varied or mixed.'