private mass
/ˌprʌɪvɪt ˈmas/noun
A mass celebrated without a congregation, as in a private oratory. Formerly also derogatory (in early Protestant use): †a mass at which the congregation, though present, is not allowed to take communion ( obsolete ).
Origin
Mid 16th century; earliest use found in Richard Taverner (?1505–1575), translator and evangelical reformer. From private + mass, after post-classical Latin missa privata.