Ysida

Ysida was an uninhabited class P planet, located in the Delta Quadrant close to the boundary with the Beta Quadrant. Much of its surface was covered by an ocean of high-density vapor, with a scattering of desert islands and rocky reefs. The planet was home to large eels. (PRO: "Last Flight of the Protostar, Part II", "A Tribble Called Quest")

In 2374, the USS Protostar, carrying Captain Chakotay and Commander Adreek-Hu, crashed on Ysida after being launched through an unstable wormhole from Solum. Due to the threat of the living construct on board the ship, the two Starfleet officers ejected the proto-core and vented the warp drive, thus marooning themselves on the planet to protect the Federation. Adreek later vanished during an attempt to restore the ship's warp core using antimatter generated by Ysida's ion maelstroms, leaving Chakotay as the sole survivor.

In 2384, Dal R'El and his friends found Chakotay and the Protostar with the help of Wesley Crusher. The young crew helped Chakotay to repair the derelict ship and restore power to the impulse engines and warp drive, allowing the Protostar to finally leave the planet. (PRO: "The Devourer of All Things, Part II", "Last Flight of the Protostar, Part I", "Last Flight of the Protostar, Part II")

The spelling of the planet's name was confirmed by Aaron Waltke. [1]
The planet was named for writer Diandra Pendleton-Thompson‘s grandmother, Daisy, who passed away during the production of the season and was an inspiration to her.