Thomasina \th(o)-masi-na, thom(a)-sina\ as a girl's name is pronounced TAH-ma-SEE-nah. It is of Aramaic origin, and the meaning of Thomasina is "twin". Feminine form of Thomas. Thomasin was the earliest form, followed by Thomasina in the Victorian era, and Tamsin a century later. The original Greek form of this name, Didymos, began as a nickname for one of the twelve disciples of Jesus in the Christian scriptures. See also Tamsyn and Tammy.

Thomasina has 14 variant forms: Tammi, Tammie, Thomasa, Thomasin, Thomasine, Thomazine, Toma, Tomasina, Tomasine, Tomina, Tommi, Tommie, Tommy and Tommye.

Baby names that sound like Thomasina are Tamasine and Tamasin.