Leg of a Triangle

Date: 04/02/2002 at 17:19:36
From: Lucy
Subject: Parts of triangles

I need to know where the name "leg" of a triangle comes from, or what 
its origin is.

Thank you for your help.

Date: 04/02/2002 at 20:45:59
From: Doctor Sarah
Subject: Re: Parts of triangles

Hi Lucy - thanks for writing to Dr. Math.

From Steven Schwartzman's _The Words of Mathematics, An Etymological 
Dictionary of Mathematical Terms used in English_ (Mathematical 
Association of America):

leg
from Old Norse leggr "leg," of unknown prior origin. In a right 
triangle, the two sides that aren't the hypotenuse are known as legs. 
Because there are two of them, (as opposed to the three sides of a 
non-right triangle) they are named by analogy with the two legs of the 
human body.

- Doctor Sarah, The Math Forum
  http://mathforum.org/dr.math/