The triad; three in one
A modern phonetic spelling of Trinity, referring to the Christian doctrine of the Holy Trinity. It signifies the union of three persons in one Godhead: Father, Son, and Holy Spirit. As a name, it gained popularity in the late 1990s following pop culture influences.
Less common today
Trinitey isn't in the latest US Top 1000. It last peaked at #11,430 in 2004.
US births per 5-year period, 1990βpresent (SSA data).