Green’s Dictionary of Slang

happy-clappies n.

[a derog. term that emphasizes the differences between the lower- and lower-middle-class evangelicals and the middle- and upper-class Church of England]

(orig. S.Afr.) members of an evangelical church, whose services involve a good deal of ‘audience participation’, e.g. singing, responding, clapping of hands.

Show quotations
[SA]R. Malan My Traitor’s Heart (1991) 100: Both were members of the Apostolic Church, happyclappies in South African slang—into the laying on of hands, faith healing, and speaking in tongues.
[UK]Sun. Times Rev. 12 Mar. 3: Swinging from Holy Trinity Brompton’s happy-clappies to high church.