What's a Kwaj?

Kwajalein, Republic of the Marshall Islands, is where I lived from 2000-2005.  The Marshall Islands, formerly a US Territory, are now an independent republic in Micronesia.  They lie about half way between Hawaii and Australia.  The RMI are made up of many atolls, Kwajalein being the largest.  An atoll is a circle of coral islands that surround what used to be a volcano.  The island I lived on is also called Kwajalien, Kwaj for short.