Some say Giovanni Palestrina rescued music from the church (and for the church) when the Council of Trent (1545-1563) objected to newer musical trends in which you could not even understand the words being sung. Palestrina was definitely a major influence on church choral music in his day.
"Gloria" is from the Missa Papae Marcelli, or Pope Marcellus Mass. For those interested in way more info that I can knowledgeably provide, check out Classical Notes.