Merriam-Webster's Collegiate® Dictionary, 11th Edition
SHACKLE
I. noun
Etymology: Middle English schakel, from Old English sceacul; akin to Old Norse skǫkull pole of a cart Date: before 12th century something (as a manacle or fetter) that confines the legs or arms, something that checks or prevents free action as if by fetters, a usually U-shaped fastening device secured by a bolt or pin through holes in the end of the two arms, a length of cable or anchor chain of usually 15 fathoms,
II. transitive verb (shackled; shackling)
Date: 15th century
1. to bind with shackles ; fetter , to make fast with or as if with a shackle, to deprive of freedom especially of action by means of restrictions or handicaps ; impede , see: hamper shackler noun