Debaptism is of course a noun derivation using the productive prefix de- meaning ‘remove’ or ‘opposite’, as in e.g. decaffeinated, decentralize, deforestation. There is also plenty of evidence for a corresponding verb debaptise, usually occurring in passive form as in be/get debaptised, and with an –ize spelling variant (i.e. debaptize), which can be used in both British and American English. Both noun and verb also regularly occur in hyphenated form, i.e. de-baptism, de-baptise/de-baptize.