A Lexicon of Saint Thomas Aquinas - Roy J. Deferrari

A Lexicon of Saint Thomas Aquinas is a Latin-lexicon (Latin → English) focussed on the vocabulary used by St. Thomas Aquinas, especially in his Summa Theologica, plus selected passages of his other works. 

It was first published in 1948 by the Catholic University of America Press, with Roy J. Deferrari as lead author, along with Sister M. Inviolata Barry and Ignatius McGuiness. 

A later reprint or edition came out in 2004 published by Loreto Publications (“Preserving Christian Publications”).