'methodicalness' originates from English, specifically formed from 'methodical' + the suffix '-ness', where 'methodical' derives from 'method' plus the adjectival suffix '-ical'.

'methodical' was formed in English from 'method' (from Latin 'methodus' and Greek 'methodos') with the suffix '-ical' in the 17th century; '-ness' is an Old English/Old Germanic nominalizing suffix (Old English 'næss'/'nes'). Over time these elements combined to form the abstract noun 'methodicalness'.

Initially the roots referred to a 'way' or 'pursuit' (Greek 'methodos' = 'way of investigating'); over time the assembled English forms came to mean 'having a systematic way' and the modern compound 'methodicalness' expresses the quality of being methodical.