'manifestness' originates from Latin, specifically the word 'manifestus', where 'manus' meant 'hand' and 'festus' (in this formation) conveyed the sense of 'seized' or 'struck'.

'manifestness' changed from the Latin adjective 'manifestus' into Old French and Middle English forms like 'manifest', and the English noun 'manifestness' was later formed by adding the suffix '-ness' to denote the state or quality.

Initially, it meant 'caught in the hand' or 'seized' (literally evident); over time it evolved into the current sense of 'clearly apparent' and thus the noun came to mean 'the quality of being clear or obvious'.