'unappealingness' originates from English, specifically from the negative prefix 'un-' + 'appealing' (the adjective/participle form of 'appeal') + the noun-forming suffix '-ness', where 'un-' meant 'not' and '-ness' marked a state or quality.

'appeal' comes into English from Old French 'apeler' (to call), ultimately from Latin 'appellāre'; it entered Middle English as forms like 'apelen'/'apilen' and developed the sense 'to attract' or 'to be attractive' before 'appealing' and then 'unappealing' were formed in modern English, with '-ness' added to form the noun 'unappealingness'.

Initially, the root 'appeal' meant 'to call to or address' (from Latin), and over time shifted toward senses of 'attract' or 'evoke interest'; 'unappealingness' thus now denotes 'the absence of attraction or appeal'.