Trinity comes from the Latin trinitas, meaning "three" or "triad" — referring to the Christian concept of God as Father, Son, and Holy Spirit. The name carries direct theological weight.
Trinity rose dramatically in the late 1990s, possibly aided by the character Trinity in The Matrix (1999). It peaked at #36 in 2007 and has been declining gradually. Today it sits in the U.S. top 175 — still very much in use, particularly in religious families.
Trinity reduces to six — the number of triune harmony.