Its source is a Welsh expression meaning "Sea fortress."
This boy's name is used in Welsh.
The modern names that derive from Myrddin are very controversial, and some authorities insist they were created by mistake.
In British legend, the wizard who tutored King Arthur was known as Myrddin Emrys. Writers translated this into Latin as Merlin Ambrosius, and into English as Mervyn, possibly in reference to the Welsh name Merfyn. Their mistake was believing that the first part of the name (Myrddin) was personal. It was, in fact, a place name -- the Welsh name for the seacoast town of Carmarthen. Emrys was the personal name -- a Welsh version of Ambrose.
So ''Ambrose of Carmarthen'' is possibly the best interpretation of the legendary Merlin's name. If it seems an insufficiently formidable name for a wizard, consider the meaning of Ambrose -- ''immortal.''