Go under the knife

Origin

The phrase "go under the knife" is a vivid, literal description of surgery, emerging as modern medical practices became more common and sophisticated. The "knife" refers directly to a surgeon's scalpel or other cutting instruments, while "under" places the patient in the vulnerable position on an operating table, fully subject to the procedure. This straightforward imagery, emphasizing the invasive nature of surgical intervention, quickly became a widespread and somewhat dramatic euphemism for undergoing an operation, reflecting the public's direct understanding of what surgery entailed.