Several 23rd century kleegats

The kleegat was a three-sided, bladed Capellan weapon used by tribal warriors on the planet Capella IV. It was highly effective at any distance up to a hundred yards, and was said to be as effective against a man as a phaser.

In 2267, a Capellan used a kleegat to kill Grant, a Starfleet security officer, and Kras, a Klingon agent. (TOS: "Friday's Child")

According to the final draft of the script, dated 18 May 1967: "We see a tribesman demonstrating the use of a boomerang-shaped weapon. Startling speed (film speed-up) as he throws it at a weed target in the distance, camera cutting to reveal the weapon neatly severing the weed exactly at the mark! An extremely long throw, with savagely expert aim."
It is very similar in both name and design to the Klingon kligat, seen in TNG: "Hide and Q".