ETYMOLOGY
from Latin credulus (ready to believe or trust) + -ist
EXAMPLE
“… the couetous Bashaw of Aleppo, the gouernor of those parts, are contented to beare with things euen contrary to the lawes of their Alcheron, impugning altogether the Godhead and incarnation of Christ: as the Iews against his pouerty and humiliation: & for great sums of mony, & annuall entrado, suffer stil diuers friers & religious persons to entertain pil∣grims, trauellers, ignorant deuotists, superstitious papists, and simple credulists, with impudent, lying, & deceitfull relicks …”
From: The Secretaries Studie Containing New Familiar Epistles
By Thomas Gainsford, 1616
Lexicophilia 