Пять минут в вики. И при чем тут церковь? )

It is commonly believed that the term missionary position arose in connection with English-speaking Christian missionaries, who supposedly encouraged the sexual position in new converts in the colonial era.[5] However, the term probably originated from Alfred Kinsey's Sexual Behavior in the Human Male through a confluence of misunderstandings and misinterpretations of historical documents.[6][7] The French refer to it as the 'classical' position. Tuscans refer to the position as the Angelic position while some Arabic-speaking groups call it the manner of serpents.[8]

(краткий пересказ: ходила байка, что в такой позе миссионеры трахают туземок. В печать байку запустил конкретный сексолог Кинси, до него словосочетание не встречается)