indicate the level to which a name has been verified.
Meaning & History
Appears to be a form of Welsh Sulgwyn "Pentecost, Whitsunday" (literally "white Sunday", from (Dydd) Sul "Sunday, day of the sun" + gwyn "white, holy, blessed"). But Sul (= "sun") was also the name of a Celtic saint, commemorated in certain Welsh place names (e.g. Llandysul, Llandysilio); Sulwyn is formed from this element + -wyn, name suffix meaning "white, fair" from Welsh gwyn.