Brianna doesn't appear to derive from a saint's name. It is a relatively recent coinage (20th century) made to create a female form for the well known boy's name Brian.
Brian is an old Irish name, derived from a Celtic word meaning "high" or "noble." There are no saints of that name, but it was the name of a famous 10th century high king, Brian Boru.
Brianna has many variants. A few of these are Breanna, Bryana, Brianne and Breanne. There is also a simliar name, Brenna, which comes from a Gaelic word meaning "little drop of water."
You could be thinking of Brenda. This isn't a saint's name either and actually comes from an Old Norse word meaning "sword", but it is often linked with the Irish name Brendan (from the Gaelic for "prince") which was also the name of two early Irish saints.
Brian is an old Irish name, derived from a Celtic word meaning "high" or "noble." There are no saints of that name, but it was the name of a famous 10th century high king, Brian Boru.
Brianna has many variants. A few of these are Breanna, Bryana, Brianne and Breanne. There is also a simliar name, Brenna, which comes from a Gaelic word meaning "little drop of water."
You could be thinking of Brenda. This isn't a saint's name either and actually comes from an Old Norse word meaning "sword", but it is often linked with the Irish name Brendan (from the Gaelic for "prince") which was also the name of two early Irish saints.