'ceremoniousness' originates from English, specifically the adjective 'ceremonious', ultimately from Latin 'ceremonia' where the root meant 'ceremonial rite' or 'formal rite'.

'ceremonious' developed via Late Latin 'ceremoniosus' and Old French forms (e.g. 'ceremoniéus') into Middle English 'ceremonious'; the noun 'ceremoniousness' arose in modern English as a nominalization of that adjective.

Initially it was used in senses directly tied to formal religious or public rites ('relating to ceremony'), but over time it broadened to mean the general quality of being formal or overly formal — the modern sense of 'the state or quality of being ceremonious'.