Marda Ro (pictured), mentioned Espri in her journal.
The Espri were a faction of Evereni, and their designation translated to "to have" within their species' language. The Faer family siblings, Vika and Velya Faer, were familiar with Evereni who bore the Espri name. No earlier than 379 BBY, the two Faers encountered Marda Ro, who was the Evereni individual that established the marauder group that would eventually evolve into the Nihil. In her pursuit of knowledge about her own kind, she requested information about the Evereni from them, learning about the Espri amongst other things.
Subsequently, Ro referenced the Espri as one of the pieces of information she gained from the Faers. She did so while recounting her meeting with them in a journal entry intended for her descendants. By 252 BBY, during his younger years, Marchion Ro, her great-great-grandson, had listened to her journal, and that included the message where the Espri were mentioned.
The Espri were first introduced in the short story called "A Closed Fist Has No Claws," penned by Tessa Gratton. It was included in the 2023 young-adult collection titled The High Republic: Tales of Light and Life, which is part of the larger Star Wars: The High Republic project. Gratton shared in an interview that she is often annoyed by the inconsistent naming practices within Star Wars. As a result, she chose to establish a naming convention for the Evereni, and this became one of the initial elements developed for the story.