Twin and supplanter
A rare compound name combining the Greek-Aramaic Thomas and the Hebrew James. Thomas signifies a twin, while James is derived from Jacob, meaning one who follows or supplants.
Less common today
Thomasjames isn't in the latest US Top 1000. It last peaked at #6,906 in 1996.
US births per 5-year period, 1990βpresent (SSA data).