Ecclesiastical describes a thing having to do with the (Christian) church, and is based on the old Greek name for the church. In antiquity, the early Christian church co-opted the name of the Athenian political assembly of voting citizens and called itself the ekklesia (ἐκκλησία), meaning "assembly." Ekklesia combines the words ek (ἐκ), meaning "out," and kalein (καλεῖν), meaning "to call," so the assembly or church members are literally those who are "called out." Since the church, or the ekklesia (ἐκκλησία), are the "called out," then anything dealing with the church is ecclesiastical.