Submitted Name Save Gender Feminine Usage English (Archaic), Cornish (Archaic) Other Forms FormsThomasina, Tomasyn, Thomasine, Tamsin, Thomasyn (Cornish) Edit Status Status [history·contributorshide contributors] Added 2/1/2008 by anonymous Edited 11/29/2020 by Frollein Gladys Meaning & History Feminine form of THOMAS. Thomasin was one of the most popular girls names in the Middle Ages.