I think that D&D clerics and paladins, as originally presented, are two mechanical variants on the one idea: a heavily armed and armoured worker of miracles (heal with a touch, dispel evil spirits, etc). The miracle-working knight (or king) is something that is found in mediaeval legend. D&D immediately makes them weird, though, by having them enter dungeons in search of loot, rather than doing the sorts of things that mircale-working knights actually do in the legends that they belong to.
The introduction of variant clerics, from DDG on and especially with the old "specialty priests" that have informed both 3E and 5e, resulting in not all clerics being heavily armed and armoured and some clerics being more like variant MUs (invokers, in 4e terms), has largely severed the connection between the class and the original archetype/exemplar/trope.