Tift
Merritt's full name is
Catherine Tift
Merritt. Tift has been used as a given name for both males and females within her family:
http://www.bostonglobe.com/arts/music/2012/10/04/tift-merritt-seizes-moment-with-traveling-alone/gcMcF0FCdXHjz2SasitvvL/story.html
Tift is almost certainly from a surname. There is a Tift County in
Georgia named after a man who had Tift as a last name. I have found a webpage which claims that the surname Tift is a form of Toft or Taft:
http://www.surnamedb.com/Surname/Tift
According to Reaney &
Wilson's
A Dictionary of English Surnames, Toft and Taft are from an English place name which meant "crofts" or "homestead". However, that dictionary does not include Tift as a variation of Toft and Taft, so I have no knowledge one way or the other whether the idea that Tift is from the same source is correct.