Presbyterian (adj., n.)

1640, in reference to the Scottish church governed by elders (as opposed to bishops) and holding a modified form of Calvinism, from presbyter "an elder in a church" (1590s), from Late Latin presbyter "an elder," from Ecclesiastical Greek presbyteros "one that presides over assemblies or congregations," noun use of an adjective meaning "elder (of two), old, venerable, advanced in life," comparative of presbys "elderly, aged" (see presby-). 

Also used generally (with lower-case p-) of any system of ecclesiastical government by church elders. Presbyterial was used from c. 1600 in the sense "of or pertaining to a presbytery;" also from 1590s as "presbyterian" (adj.). Related: Presbyterianism.