'comfortableness' originates from English, specifically formed from the adjective 'comfortable' plus the suffix '-ness' which turns adjectives into nouns.

'comfortable' changed from Old French 'confortable' (and Medieval Latin 'confortabilis') ultimately from Latin 'confortare'; the English adjective 'comfortable' developed from these sources, and 'comfortableness' was later formed by adding '-ness' to 'comfortable'.

Initially the Latin root 'confortare' meant 'to strengthen greatly' or 'to give strength/comfort'; over time the word evolved into the sense of 'providing ease or relief' in Modern English, which is reflected in 'comfortable' and 'comfortableness'.