The Collaborative International Dictionary of English v.0.48:

Undershirt \Un"der*shirt`\, n.
   A shirt worn next the skin, under another shirt; -- called
   also undervest.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Undervest \Un"der*vest`\, n.
   An undershirt.
   [1913 Webster]