A cutlass was a 18th century sword.

In 2267, after being convinced that simply hanging Captain Kirk would be too boring, Trelane decided to have a hunt. He chased after Kirk brandishing a cutlass. During the fight, Kirk managed to grab it off him, and tried to stab him with it, but Trelane vanished only to return after the blade had been removed, pointed, and the sword came back to him. At the end of the hunt, Kirk called his bluff and grabbed the sword and broke it over his knee. (TOS: "The Squire of Gothos")

In 2268 when the Beta XII-A entity transformed matter into primitive weapons, one of them was a cutlass that Kirk took from a defeated Klingon. He later left the weapon in the transporter room when he went to speak with Kang. (TOS: "Day of the Dove")