Plural of diocesan; people who belong to or are members of a diocese, or priests serving a diocese.
From Medieval Latin 'diocesanus' + English plural '-s,' formed as a noun from the adjective, documenting ecclesiastical communities from medieval times onward.
In medieval and modern church records, you'll see 'diocesans' used for both the clergy and the laypeople of a diocese—it's one of those words where the grammatical category blurs, similar to how 'English' can mean the language or the people.
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