Meaning and name origin
Garreth \g(a)-rre-th\ as a boy's name is of Celtic origin, and the meaning of Garreth is "gentle". Garreth is a variant of Gareth (Celtic): sir Gareth, noted for his modesty and bravery, was a knight of King Arthur's Round Table. Also a variant of Garret: surname derived from Gerald and Gerard, used as a first name and dating from the Middle Ages.
Garreth is not a popular first name for males and an equally uncommon surname or last name for all people (2000 U.S. Census).
Displayed below is a comparison of the popularity of the boy name Garreth and its variant forms. The only popular variation form ranked in the Top 1000/100 is Garret. (2014 statistics).