coupler vs vinculum

coupler

noun
  • A device that connects two keyboards of an organ together so that they play together. 

  • An electrical device used to transfer energy from one electric device to another, especially without a physical connection. 

  • Anything that serves to couple things together; but especially a device that couples railway carriages. 

  • A device used to convert electronic information into audible sound signals for transmission over telephone lines. 

vinculum

noun
  • A ligament that limits the movement of an organ or part. 

  • A bond or link signifying union. 

  • A horizontal line over the top of some of the terms in an expression, indicating that that part of the calculation is to be done before other parts. 

  • Specifically, the horizontal line between the numerator and denominator in a fraction. 

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