Is it ensure, insure, or assure?
"to climb a rope, pole, etc.," 1888, from use of shins and ankles to do so; see shin (n.). Earlier simply shin (1829). Related: Shinnied; shinnying.
also shinney, primitive form of hockey, 1670s, perhaps from Gaelic sinteag "a bound, a leap." OED suggests origin from shin ye "the cry used in the game."