Tandy \t(a)-ndy, tan-dy\ as a girl's name (also used as boy's name Tandy). Possibly a nickname for Andrew (Greek) "man, warrior". However, the Latin-derived English word "tandem" is also a possible source, as well as the Old Norse term "tandr", meaning "fire". Also possbly a modern name based on Sandy or Mandy with a T-. Actresses Jessica Tandy, Thandie Newton.
For more information, see also the related name Tansy.