an ecclesiastic attached to the chapel of a royal court, college, etc., or to a military unit.
2.
a person who says the prayer, invocation, etc., for an organization or at an assembly.
Origin: before 1100;Middle Englishchapelain < Middle French < Late Latincappellānus custodian of St. Martin's cloak (see chapel, -an); replacing Old Englishcapellan < Late Latin, as above
a Christian clergyman attached to a private chapel of a prominent person or institution or ministering to a military body, professional group, etc: a military chaplain; a prison chaplain
[C12: from Old French chapelain, from Late Latin cappellānus, from cappellachapel]
mid-14c., from O.Fr. chapelain "clergyman," from M.L. cappellanus "clergyman," originally "custodian of St. Martin's cloak" (see chapel). Replaced O.E. capellane, from the same M.L. source.