'atrosanguineous' originates from Latin, specifically the elements 'ater' and 'sanguineus', where 'ater' meant 'black' and 'sanguis' (the root of 'sanguineus') meant 'blood'.

'atrosanguineous' is a Neo-Latin/medical compound formed from the prefix 'atro-' (from Latin 'ater') + the adjective 'sanguineous' and entered English in medical usage with essentially the same combined meaning.

Initially it literally combined the meanings 'black' + 'of blood' to indicate 'black-blooded' or 'dark and bloody'; this specialised medical sense has been retained in modern usage.