Merry does work as a full name, too similar to
Joy for me to feel differently. I do not hear a difference between
Merry and
Mary. I would pick
Holly out of
Merry, Merrily and
Holly.
Merry might have not caught on because it might be considered a butchered form of a classic girl name - it also reminds me quite a lot of
Christmas. The commercialization of the holiday might have been turnoff for some. The other thing is that it might sound too sappy, and not as natural as other names with the same meaning.
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