How do I use just my first name on Facebook?

[myillusoryentity]

I think what you can do is split your first name into two parts. For example: Dav id (Dav being the first name and id being the last name), Jess ica (Jess being the first name and ica being the last name)

I've seen a few people do this. It might work if you do it once since Facebook monitors name changes, and they will disable this feature if you keep changing your name.