According to some rumors, the Paraelemental Planes were different in a distant era when the Elemental Planes were arranged differently. During that time, supposedly, Fire and Water combined to create a Paraelemental Plane of Steam (home to the wavefires) and Earth and Air combined to create a Paraelemental Plane of Dust.
List of Paraelemental Planes
- Paraelemental Plane of Ooze (between Earth and Water)
- Paraelemental Plane of Ice (between Water and Air)
- Paraelemental Plane of Smoke (between Air and Fire)
- Paraelemental Plane of Magma (between Fire and Earth).
It was not specified what the other two original planes were in the era of Steam and Dust, but it can be presumed they were equivalents of either Smoke and Ooze or (more likely) Ice and Magma.
In the early days of Dungeons & Dragons, the "para-elemental" planes were different: Vapor instead of Ooze, Dust instead of Smoke and Heat instead of Magma. This had changed to the current outlook by late 1st Edition.