Perhaps this is more well known than I imagined, but I found this fascinating. The word ‘chaplain’ comes from 8th-century pre-battle liturgical practices:
Cappellani [chaplains] originally came from the cappa [cloak] of blessed Martin; the Frankish kings commonly took it with them in battle because it helped them to victory; because they carried it and cared for it with other saints’ relics, clerics began to be called chaplains.
This means that chaplaincy has a decidedly military origin: both in St. Martin, himself a former soldier turned Bishop, and in the use of his half-cloak, venerated as a relic by medieval kings. Today, chaplains in many contexts still care in the name of Christ at the service of soldiers, doctors, prisons, and ultimately, the church.
Thank God for them.
Source: Andrew Totten, “Moral Soldiering and Soldiers’ Morale,” in Military Chaplaincy in Contention (Surrey: Ashgate, 2013), 22.