Many Dwarves from the Prime Material Plane were unwillingly sent to the Plane of Faerie where they underwent a transformation into the first Gnomes.
Having been thrust from the Prime Material Plane by the Primordials, numerous dwarves found themselves lost on Faerie.
The newly formed gnomes began to spread out and begun creating homes and settlements of their own in Faerie, splitting into three distinct races.
The dawn gnomes became their own people, splitting off from the group and developing their own magics and racial features distinct from other gnomes.
Re-developing the darkvision of their dwarvish ancestors, the deep gnomes finish their adaptations to their chosen environment and become their own race.
During the Age of Light, the ancestors of the gnomes dwelled within Faerie, having recently been turned from dwarves.