Basic Guidelines For English Spellings
READ THESE ARTICLES
1rare A person, especially an official, who records something in a register; = "registrar".
2A person who submits something for registration; a person who is registered for something.
Late 15th century; earliest use found in John Lydgate (c1370–c1449), poet and prior of Hatfield Regis. From register + -er. Compare post-classical Latin registerarius.