Naming is not easy. It's a hard thing to name another human being. Lesley and I put in a lot of consideration into both Thomas' and Karis' names.
For those who don't know, 'Karis' is Greek for grace and her middle name, 'Sophia', is Greek for wisdom. Two virtues that we wish upon her.
'Thomas Zane' was decided upon after much deliberation. In fact, Lesley and I employ 'bracketology' to help come up with a name. We had a March Madness tournament of 64 male names.
'Thomas' means twin, so it was not chosen for its meaning, but rather for other great Thomases that have come before (particularly philosopher/theologians):
Thomas Aquinas, Thomas a Kempis, Thomas Reid, etc.
'Zane' was chosen in part for its meaning. It means God's gracious gift. It was also chosen since we like names that start with letters not typically used.
In addition to the merits of each name on its own, we also like the combination both in full names and in the abbreviated 'T.Z.'.