It was never required to be named after a saint, but many parents chose to name their child after a siant. That saint became their child's patron, and is thought to look after the child in a special way. It is the same with confirmation names as well.
There is no saint in the Catholic tradition named Saint Tatum. The name Tatum is not a commonly recognized saint's name.
No, there is no saint named Kennedy.
I can find no saint named Chelsea.
There is no saint named Shined.
I can find no canonized saint named Cassandra.
There is no saint named Ellen. However, the name derives from Helena and there is a saint named Helena
No, Muireann is not a saint name.
I can find no saint named Carla. However, the name derives from Carol which derives from Carolus - or Charles and there is a Saint Charles.
There is no saint named Ashling.
There is no canonized saint by that name.
There is no saint named Lee.
There is no saint named Macy.