'antiquatedness' originates from Latin, specifically the word 'antiquatus' (the past participle related to 'antiquare'/'antiquus'), where 'antiqu-' meant 'old' and '-atus' indicated a past state; the English noun was formed by adding the suffix '-ness' to 'antiquated'.

'antiquatedness' changed from the Latin word 'antiquatus' (via Medieval/Latin forms and through influence on French/English adjectival forms) into the English adjective 'antiquated' and was later nominalized as 'antiquatedness' by adding '-ness'.

Initially it related to being 'made old' or simply 'old' (from Latin), but over time it evolved into the modern English sense of 'the state or quality of being old-fashioned or obsolete'.