Yan

From Memory Alpha, the free Star Trek reference.

A yan is a type of ceremonial bladed weapon used by some Klingon warriors. Kurn had a pair of yan hanging in his office aboard the IKS Hegh'ta, as had Lursa and B'Etor aboard their ship. (TNG: "Redemption")

Like his brother, Worf also kept two crossed yans in his quarters aboard the USS Enterprise-D. (TNG: "Reunion", "Night Terrors")

During his exercise program on the holodeck, Worf and K'Ehleyr used a pair of yans to defeat computer-generated opponents. (TNG: "The Emissary")

Duras utilized a yan in his duel with Worf in 2367. He was killed by Worf and his bat'leth. (TNG: "Reunion")

Governor Vagh of Krios also had two crossed yans on display in his office. (TNG: "The Mind's Eye")

These weapons were never named on-screen.