The English word chaplain descends, by way of the medieval Latin term cappellanus, from cappa, the short cloak associated with Saint Martin of Tours. According to the tradition behind the word, a relic believed to be the cloak was kept among the treasures of the Frankish kings, housed in a private oratory, and the priest responsible for guarding it and for the kings devotions was called its keeper, the cappellanus, while the oratory itself came to be called a cappella, a chapel. From that specific office the word widened to mean any priest attached to a household, a court, a regiment or an institution rather than to a parish of his own, someone whose ministry followed a group of people rather than a fixed territory.
That distinction, ministry that follows an institution rather than a congregation, is still what defines chaplaincy today, even though almost everything about how it is organized has changed. A modern chaplaincy department in a hospital, prison, university, port or branch of the armed forces is credentialed by the institution itself rather than by ownership of a parish, commonly serves people of several religions or none through a multi-faith team, and in a growing number of institutions now includes credentialed non-religious pastoral carers working alongside ordained chaplains in the same department, a development this atlas records separately as non-religious pastoral care. Credentialing requirements, reporting lines and the balance between religious and secular staff vary widely by country and by institution, and no single global standard governs any of it.