ASSIDUUS, or ADSIDUUS, among the Romans, denoted a rich or wealthy person. The word in this sense is derived from as assis, q. d. a moneyed man. Hence we meet with assiduous sureties, assidui fidejussores, answering to what the French now call city sureties or securities, cautions bourgeois.
When Servius Tullius divided the Roman people into five classes, according as they were assessed or taxed to the public, the richer sort who contributed asses were denominated assidui; and as these were the chief people of business who attended all the public concerns, those who were diligent in attendances came to be denominated assidui.