The name Elder is a boy's name . Elder and discussed in our forums with posts like "Imaginary Birth Announcements!".
From the experts:
Anyone who's seen "The Book of Mormon" or visited Utah knows this as the title taken by male Mormon missionaries during their term of service. We'd advise anyone who lives somewhere with any significant Mormon population to avoid it for that reason.
That said, Elder does have some history as a boys' name, especially in Latin America, where the stress is on the second syllable. The "el-" sound has become extremely fashionable, so we wouldn't be surprised if this started climbing up the charts.