Is it ensure, insure, or assure?
1580s, "made of wire," from wire (n.) + -y (2). As "resembling wire," From 1590s; sense of "lean, tough" is first recorded 1808. Related: Wiriness.
wiry wir·y (wīr'ē)adj. wir·i·er, wir·i·est
Resembling wire in form or quality, especially in stiffness.
Sinewy and lean.
Filiform and hard. Used of a pulse.