What are the settlers of Kuwait from?

Most original settlers were Pure blooded arabians that came from various places in the Arabian Peninsula.
Pure Blooded arabians are the true settlers of the Arabian Peninsula since the dawn of time, they proclaimed their purity by never mixing with anything but other pureblooded arabs, no, that wasn't inbreeding if that's what you are wondering, There are literally thousands of different bloodlines in each original tribe.

Most came from Najd and other places from KSA and a few from Qatar.