'aperiodicity' originates from English by combining the prefix 'a-' (meaning 'not') with 'periodicity', which itself comes from 'periodic' + the noun-forming suffix '-ity'.

'periodicity' derives from 'periodic' (from Medieval/Modern Latin 'periodicus'), which ultimately comes from Greek 'periodos' ('peri-' meaning 'around' + 'hodos' meaning 'way' or 'course'). The negative prefix 'a-' (from Greek 'a-' or 'an-') was added in English to form 'aperiodic', and the abstract noun-forming suffix '-ity' produced 'aperiodicity'.

Initially the elements meant 'around/way' (in 'periodos') and later 'a regularly recurring interval'; 'aperiodicity' has consistently come to mean 'the absence of such regular recurrence'.