tied vs under obligation

tied

adj
  • Conditional on other agreements being upheld. 

  • Restricted. 

  • a cover having a stamp where the postmark cancellation overlaps the stamp. 

  • Having walls that are connected in a few places by a single stone overlapping from one wall to another. 

  • Provided for use by an employer for as long as one is employed, often with restrictions on the conditions of use. 

  • Closely connected or associated. 

  • That resulted in a tie. 

under obligation

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