Sui generis
In sociology, the "sui generis" is what has been externalized, then internalized in the overall public and becomes a part of society that simply exists in its construct. It is not something that is not thought to have been created, because it is imbedded in everyone's way of thinking and being. Instances include the idea of love, or going to school, or clothing belonging to a specific gender. These examples are "sui generis" for they simply exist in society and are widely accepted without thoughts of where they come from or how they were created.
Seia gens
The nomen "Seius" is derived from the name of Seia, the goddess of sowing. Chase classifies it among those gentilicia that either originated at Rome, or cannot be shown to have come from anywhere else.