The name Eilidh is a girl's name of Scottish origin meaning "sun, radiant one". Eilidh and is often added to lists like British Girl Names and discussed in our forums with posts like "Girls Makeover - Two Middles".
From the experts:
Long popular in Scotland, this attractive name is widely considered to be the Gaelic version of Helen. After the Normans introduced it into the British Isles, it was transformed into Evelyn. It has rarely been heard in the U.S., where the spelling would be sure to cause endless pronunciation problems -- it's ay-lee.