The Collaborative International Dictionary of English v.0.48:

Stalwart \Stal"wart\ (st[o^]l"w[~e]rt or st[add]l"-; 277),
Stalworth \Stal"worth\ (-w[~e]rth), a. [OE. stalworth, AS.
   staelwyr[eth] serviceable, probably originally, good at
   stealing, or worth stealing or taking, and afterwards
   extended to other causes of estimation. See Steal, v. t.,
   Worth, a.]
   Brave; bold; strong; redoubted; daring; vehement; violent. "A
   stalwart tiller of the soil." --Prof. Wilson.
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         Fair man he was and wise, stalworth and bold. --R. of
                                                  Brunne.
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   Note: Stalworth is now disused, or but little used, stalwart
         having taken its place.
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