'attriteness' is formed in Modern English by adding the noun-forming suffix '-ness' to 'attrite', which itself ultimately derives from Latin 'attrītus' (past participle of 'atterere'), where 'ad-' meant 'to' and 'terere' meant 'to rub'.

'attrite' comes from Latin 'attrītus' / Late Latin 'attritio' meaning 'a rubbing or wearing away'; this passed into Middle English via Old French/Latin influences (e.g. Middle English 'atriten', 'attrition'), and in Modern English the derived noun 'attriteness' was formed by productive use of '-ness'.

Originally related specifically to physical rubbing or wearing away ('to rub against' or 'to wear down'); over time the sense broadened to include metaphorical wearing down (loss of numbers, strength, morale), which is reflected in modern uses.