from the GNU version of the Collaborative International Dictionary of English
- n. the authority claimed by the ministry in some Christian churches to administer the discipline of the church, and to grant or withhold its privileges; -- so called from the declaration of Christ, “I will give unto thee the keys of the kingdom of heaven.”
Sorry, no etymologies found.
According to Febronius (cap. i), the power of the keys was entrusted by Christ to the whole body of the Church, which holds it principaliter et radicaliter, but exercises it through her prelates, to whom only the administration of this power is committed.