While the conciliar teaching had benefited from developments that had taken place in biblical, patristic, liturgical and ecclesiological studies since the First Vatican Council, it had still to convey the Church’s magisterial teaching on Our Lady, which had been handed on and enriched under the guidance of the Holy Spirit. On the one hand, the papal magisterium from the time of Blessed Pius IX onwards had continued developing the teaching about Mary’s active collaboration in the work of the redemption and Pius XI had publicly used the term “Coredemptrix” to describe this role. On the other hand, there was a distinctive concern on the part of many to promote in the council documents language that could be more easily understood by our separated brethren.
Calkins, Arthur Burton
"Marian Coredemption as an Impetus to Marian Devotion,"
Vol. 65, Article 10, Pages 233-276.
Available at: https://ecommons.udayton.edu/marian_studies/vol65/iss1/10