Special Agent Seeley Booth
Due to its -ley ending and its obscurity, Seeley started life in the U.S. fairly unisex. It was used 5 times in 1914, 6 in 1924 on just boys. Then it reappeared to be used 5 times in 1996 and 7 times in 2007 on just girls. 2009 and later it was used on both genders and has been increasing in popularity, but it is clearly more popular for boys, being used 36 times in 2015 but only 15 for girls. The sudden interest in this name and consistency of use in the 2000's is likely in thanks to Seeley Booth, played by David Boreanaz in the TV show Bones. The show began airing in 2005, but it wasn't until 2009 that Seeley resumed use on team blue. Temperance had a similar revival at the same time and then took off running.
Seeley is an Old French surname meaning "blessed," and historically has been spelled Sealey, Seelye and Seely. Real life namesakes include Seeley G. Mudd, professor, physician and philanthropist, the son of Seeley Wintersmith Mudd, mining engineer. Seeley comes from the same root as German name Selig, ultimately a Yiddish word meaning "happy" and "blessed."