What’s Up With the Title?
On a very basic level, the title serves as an advertisement for the book and clues us in to what to expect from it. A cay is a small island in the ocean that forms on a coral reef. From this we can gather that the novel is probably an adventure story, most likely involving ships or a castaway. We also know that the cay is probably where the most important action in the book will take place. The title, therefore, orients us as a reader.
On a deeper level, the cay also pushes us to think about islands more generally. An island is a self-sustaining little world, an isolated ecosystem. We can interpret the cay as a mini version of the real world; that is, the events and ideas we see dramatized on the cay (acceptance, tolerance, sacrifice, love) can also be applied to life in the outside world.
"Cay" can also be pronounced "key" – as in the Florida Keys. This suggests to us that the author probably thinks what happens on the cay is pretty darn important – maybe even the "key" to life in the real world. Pretty cool, huh?