In the Middle Ages, a childe or child [Old English Cild > "Young Lord"] was the son of a nobleman who had not yet attained knighthood, or had not yet won his spurs. As a rank in chivalry, it was used as a title, e.g. Child Horn in King Horn, as a male progressed through the positions of squire and then knight.
The term is now obsolete, but is still well known from poetry, such as Robert Browning's Childe Roland to the Dark Tower Came and Lord Byron's Childe Harold's Pilgrimage.
In the local dialect of North East Scotland known as Doric a Childe (pronounced cheeil) is the name used that may be directly translated as chap or fellow or man in English . For example, a working childe was a working man or chap . A dour childe is dour fellow for example.
The term is used to apply to an expected next stage in human evolution in the Childe Cycle novels by Gordon R. Dickson.
Childe in Stephen King's The Dark Tower is, in Roland Deschain's own words, "...a term that describes a knight - or a gunslinger - on a quest. A formal term, and ancient. We never used it among ourselves...for it means holy, chosen by ka. We never liked to think of ourselves in such terms, and I haven't thought of myself so in many years." (p. 859, The Dark Tower VII: The Dark Tower, Pocket Books, 2006 ed.)
The term also exists, albeit with a different meaning, in the roleplaying system Vampire: The Masquerade and various spin-offs. It signifies the "offspring" of a vampire, while the creating vampire is called "Sire".