'stolidness' originates from English, specifically the adjective 'stolid' plus the noun-forming suffix '-ness' (Old English '-nes'), where the suffix indicated 'state' or 'quality'.

'stolid' originates from Latin, specifically the word 'stolidus.' The Latin 'stolidus' passed into Old French as 'stolide' and later into English as 'stolid' (17th century); combining this English adjective with the suffix '-ness' produced the noun 'stolidness'.

Initially Latin 'stolidus' meant 'dull, insensitive (mentally)', but over time the word in English shifted toward 'calm, impassive' and 'stolidness' now denotes 'the quality of being calm and unemotional.'