A priest who hears confessions, or a manual or book providing instruction on hearing confessions and administering penance.
From confess + -ionary (from Latin -ionarius, variant of -arius agent suffix). This suffix pattern created words like 'missionary,' 'functionary,' and 'luminary,' typically denoting people associated with a particular role or belief.
Confessionaries as how-to books reveal medieval concerns—they're obsessively detailed about which sins are serious, whether thinking about sin counts as committing it, and how to handle wealthy donors' confessions tactfully, showing theology as practical admin.
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