Yuen was the name of a member of the Maquis called out by Michael Eddington during his last stand against the Jem'Hadar on the planet Athos IV in 2373.

Eddington gave orders to the names Crenshaw, Yuen, Stiles, and Dimitris in an attempt to make it appear that more than he was fighting against the Jem'Hadar. Specifically, Eddington ordered Yuen and Crenshaw to circle around to the left of the Jem'Hadar. (DS9: "Blaze of Glory")

This character was only mentioned in dialogue.
Given the nature of the situation, this name may have been either made up or an actual Maquis he knew.
According to the script, the pronunciation for Yuen was " YEW-EN (equal emphasis on both syllables)" [1]
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