Going under the knife

Origin

The phrase "going under the knife" graphically illustrates the direct and invasive nature of surgery, where the surgeon's scalpel, the "knife," is the essential tool for making incisions. This idiom became widely used in the early 20th century as surgical practices advanced and became more common, moving from last-resort interventions to more routine medical procedures. It powerfully conveys the vulnerability of the patient and the precise, often dramatic, act of an operation involving cutting instruments.