drill rig vs drilling rig

drill rig

noun

  • An oil rig. 

  • Used other than figuratively or idiomatically: see drill, rig. 

drilling rig

noun

  • An oil rig. 

  • Used other than figuratively or idiomatically: see drilling, rig. 

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