The phrase “jaw-dropping” has risen, with jaw-dropping suddenness, in recent times. We ran a Google Ngram data crunch. Here’s the result:
The jaw-dropping rise began in the 1980s. Here’s a look at the portion of that same graph, beginning with the 1970’s (the 1970’s itself was an era of jaw-droppingly small usage of the phrase “jaw-dropping”):
BONUS: A medical research report called “Dropped jaw—mandibular neurapraxia in the dog” was published in 1976, in the Journal of Small Animal Practice.