The next surname family?
Surnames of the British Isles are classic source of American boys' names -- just ask any Russell, Douglas, or Warren. Today, almost any surname ending in -er or -n is a potential crossover target, for boys and girls alike.
Once a name crosses over in a big way, it paves a road for other names with a similar sound. Madison, for instance, gave a leg up to Addison, and Mason to Grayson. Are there any new families of surnames ready to make the same leap? Maybe one. I wrote recently about the rise of Finnegan for boys, and in recent months I've encountered more and more girls with names like Madigan, Carrigan and Merrigan.
The -gan names seem to have all the ingredients for popularity. Their jaunty Irish style makes them perfect siblings for a Kennedy or McKenzie. (Most -gan names are Anglicizations of Irish names which in turn came from diminutives of first names. E.g. Finnegan from the Gaelic Ó Fionnagáin, meaning "descendant of Fionnagán," a diminutive of Fionn, which means "pale." Got it? No? No matter. After all, who ever cares that Campbell comes from the Gaelic for "crooked mouth"?) The names also offer a rolling rhythm that feels comfortable in this age of Emersons and Donovans. And to top it off, many of them are nickname-ready. Parents of girls in particular flock to 2-for-1 names with a formal, androgyous full version and a cuddly girlish nickname. Addison/Addie, meet Carrigan/Carrie.
Here's my list of likeliest -gan candidates. As with -son names, the male/female potential is determined largely by the roots, so Brannigan is a likelier choice for boys than Nelligan.