A Crypto-pagan is a pagan who maintains the pretense of adherence to a non-pagan (i.e. Abrahamic) religion while continuing to observe their own religious practices in private. The term stems from the Greek word kryptos, meaning 'hidden' or 'secret'. This may be in response to a perceived danger of rejection by society, or of formalised persecution by an established religious orthodoxy.
In an article entitled The Corpus Areopagiticum as a Crypto-Pagan Project, Tuomo Lankila of the Universities of Helsinki and Jyväskylä argues that the Corpus Areopagiticum, an ostensibly Christian text attributed to Pseudo-Dionysius the Areopagite, was in fact written by Damascius, the last head of the pagan Neoplatonist school of Athens. The article suggests that the work was written "in order to resurrect more easily the polytheistic religion in better times".
The process of the Christianization of Europe typically involved Christian missionaries managing to convert a King or other ruler who then proclaimed his kingdom to be Christian. It certainly took several generations for Christianity to become truly established in the whole society, with many people - especially in rural and outlying areas - clinging for long to their ancestral religion, deemed "Pagan" from the Christian point of view. With the Church establishing its hierarchy and a network of parish priests, such practices were increasingly driven underground. Alternately, the Church in some cases gave some wide-spread practices a Christian guise, for example attributing annual processions or rites, dedicated to a local deity, to a Christian Saint instead; it is likely that in many such cases the formally-Christian people continued for some generations to invoke the original deity.
In modern society, particularly in regions of strong conservative religious belief, contemporary pagans will sometimes also seek to present the impression of conformity to the mainstream in order to mitigate the risk of ostracism or persecution. Many refer to this as "staying in the broom closet", a reference to an LGBTQ person remaining "in the closet" to hide their sexual or gender identity.
In Wicca, as presented by Gerald Gardner, traditional laws instruct practitioners to conceal their practices and religious paraphernalia by using innocuous substitutes which could easily be explained away in case of discovery: