During the course of my search into the origins of ‘Resurrection Sunday’ I found some interesting information, but mainly to do with the name ‘Easter’:
The naming of the celebration as “Easter” seems to go back to the name of a pre-Christian goddess in England, Eostre, who was celebrated at beginning of spring. The only reference to this goddess comes from the writings of the Venerable Bede, a British monk who lived in the late seventh and early eighth century. As religious studies scholar Bruce Forbes summarizes:
“Bede wrote that the month in which English Christians were celebrating the resurrection of Jesus had been called Eosturmonath in Old English, referring to a goddess named Eostre. And even though Christians had begun affirming the Christian meaning of the celebration, they continued to use the name of the goddess to designate the season.”
Bede was so influential for later Christians that the name stuck, and hence Easter remains the name by which the English, Germans and Americans refer to the festival of Jesus’ resurrection. https://theconversation.com/why-easter-is-called-easter-and-other-little-known-facts-about-the-holiday-75025
From an informative Wikipedia article https://en.wikipedia.org/wiki/Easter I found this reference to ‘Resurrection Sunday’:
Footnote  The term "Resurrection Sunday" is used particularly by Christian communities in the Middle East. Orthodox, Catholic, and all Reformed churches in the Middle East celebrate Easter according to the Eastern calendar, calling this holy day "Resurrection Sunday," not Easter. 
It seems to me that the term ‘Easter Sunday’ originated in the seventh or eighth century in England. I don’t know when the first day of the week was called Sunday, but when did Christians start to use the expression ‘Resurrection Sunday’? There seems to be a connection with Christian churches in the Middle East.
Edit: It must be obvious that the earliest christians had never heard of 'Easter' because that term did not come into existence till about the 8th century. I found this reference:
The celebration of this event, called Easter, or the Festival of the Resurrection, is the major feast day of the church. https://www.britannica.com/topic/resurrection-religion
Easter celebrates the Resurrection of Jesus Christ on the third day after his Crucifixion. The earliest recorded observance of an Easter celebration comes from the 2nd century, though the commemoration of Jesus’ Resurrection probably occurred earlier. https://www.britannica.com/topic/Easter-holiday
Is 'Resurrection Sunday' a modern invention? Or does it pre-date the name Easter?