shackle vs tether

shackle

noun
  • A U-shaped piece of metal secured with a pin or bolt across the opening, or a hinged metal loop secured with a quick-release locking pin mechanism. 

  • A link for connecting railroad cars; a drawlink or draglink. 

  • A restraint on one's action, activity, or progress. 

  • A length of cable or chain equal to 12+¹⁄₂ fathoms or 75 feet, or later to 15 fathoms. 

  • A fetter-like band worn as an ornament. 

  • A restraint fit over a human or animal appendage, such as a wrist, ankle or finger; normally used in pairs joined by a chain. 

verb
  • To render immobile or incapable; to inhibit the progress or abilities of. 

  • To shake, rattle. 

  • To restrain using shackles; to place in shackles. 

tether

noun
  • a rope, cable etc. that holds something in place whilst allowing some movement 

  • a strong rope or line that connects a sailor's safety harness to the boat's jackstay 

  • the limit of one's abilities, resources etc. 

  • The cardinal number three in an old counting system used in Teesdale and Swaledale. (Variant of tethera) 

verb
  • to connect something to something else. 

  • to connect a cellular smartphone to another personal computer in order to give it access to a hotspot. 

  • to restrict something with a tether. 

How often have the words shackle and tether occurred in a corpus of books? (source: Google Ngram Viewer )