First known use is in a personal letter from de Camp to James Randi (which is thought to still exist in Randi's archives but is not readily available for study).
The word "credophile" and the adjective form "credophilic" were used by L. Sprague de Camp at least as early as 1952 in "Lands Beyond" which he co-authored with Willie Ley (De Camp, L. Sprague & Willie Ley. Lands Beyond. NY: Rinehart, 1952, pp. 268, 272
credophile (plural credophiles)
- One who gets positive pleasure from belief and pain from doubt; one who collects beliefs not for utility but for glitter and whom, once he or she has embraced a belief, it takes something more than mere disproof to make to let go.
- One who is especially gullible.