"Form of Trinity"
The name Trinidy is commonly a female name from the "English" origin.
Trinidy is a respelling of Trinity, the English word name taken from the Christian doctrine of the Trinity, which comes from Latin trinitas, meaning threefoldness. The spelling writes the final syllable as -idy rather than -ity, the kind of phonetic respelling common in American given names. No separate meaning attaches to the Trinidy spelling.
Trinity means "Three".
The pronunciation of Trinidy is TRIN-ih-dee.