It is derived from the Greek word "kytos" which means "hollow vessel" or "container".
You'll see this suffix used in many biological terms:
* Leukocyte: White blood cell
* Erythrocyte: Red blood cell
* Lymphocyte: A type of white blood cell involved in the immune system
* Osteocyte: Bone cell
* Neuron: Nerve cell
So, whenever you see "-cyte" at the end of a word, you know it's referring to a type of cell.