-nostic is a suffix used for xenogenders relating to nostalgia. An example could be Sunnynostic. There are many subsets of -nostic genders, listed in the Nostic Genders category.
History and Flags
On 2021/8/10, Tumblr user mogai-sunflowers coined the term on Tumblr. On 2022/7/18, miraheze user Xinaphoria created the flag.