body count

The story

Coined by the U.S. military during the Vietnam War in the sense "number of killed enemy combatants", in 1962 according to Merriam-Webster.

First known use, by meaning

• from c. 1962 The number of persons or bodies counted as casualties, especially fatalities, or victims.
• from c. 1962 Of a killer, especially a serial killer, the number of people who have been killed by a given individual.
• a. 2006 The total number of sexual partners of a given individual.