'irregularly-documented' is a compound word formed from 'irregularly' and 'documented'. 'Irregularly' originates from Latin 'irregularis', where 'in-' meant 'not' and 'regularis' meant 'regular'. 'Documented' comes from Latin 'documentum', where 'docere' meant 'to teach'.

'Irregularis' transformed into the Old French word 'irregulier', and eventually became the modern English word 'irregular'. 'Documentum' evolved into the Old French 'document', leading to the modern English 'document'.

Initially, 'irregular' meant 'not following a rule', and 'document' meant 'a lesson or example'. Over time, 'irregularly-documented' evolved to mean 'not consistently recorded'.