The cork cambium, cork and secondary cortex are collectively called:
Secondary tissue in the outer cortical and epidermal layers develop from meristematic tissue called cork cambium or phellogen.
Phellogen is a couple of layers thick and made of narrow, thin-walled and nearly rectangular cells.
The outer cells differentiate into cork or phellem.
The inner cells differentiate into secondary cortex or phelloderm.
Phellogen, phellem, and phelloderm are collectively known as periderm.