'morosidad' originates from Spanish, formed from the adjective 'moroso' + the noun-forming suffix '-idad' (from Latin '-itas'). The adjective 'moroso' itself derives from Spanish 'mora', ultimately from Latin 'mōra' meaning 'delay'.

'morosidad' developed in Spanish by combining 'moroso' (from Old Spanish/Spanish 'mora' < Latin 'mōra') with the suffix '-idad' (from Latin '-itas'), producing the modern noun meaning 'state of being late' or 'delinquency'.

Initially it referred simply to 'delay' or 'the fact of being delayed' (from Latin 'mōra'), but over time it came to denote 'habitual lateness' and, in financial contexts, 'delinquency' or 'default'.