The term
proselytism originated in the context of Judaism, in which the term
proselyte referred to someone who, coming from the gentiles, had passed into the Chosen People. So too, in the Christian context, the term proselytism was often used as a synonym for missionary activity.
More recently, however, the term has taken on a negative connotation, to mean the promotion of a religion by using means, and for motives, contrary to the spirit of the Gospel; that is, which do not safeguard the freedom and dignity of the human person. It is in this sense that the term proselytism is understood in the context of the ecumenical movement: cf.
The Joint Working Group between the Catholic Church and the World Council of Churches, “The Challenge of Proselytism and the Calling to Common Witness” (1995).
(Congregation for the Doctrine of the Faith,
Doctrinal Note on some Aspects of Evangelization, Footnote 49, 2007, my emphasis)