Nahmi IV was the inhabited fourth planet in the Nahmi system.
In 2366, the Correllium fever broke out on the planet. (TNG: "Hollow Pursuits")
"NAH-me" was the planet's pronunciation from the script pronunciation guide. 
According to the Star Trek: Star Charts ("United Federation of Planets I"), Nahmi IV was listed as a member planet of the Federation in 2378.