Is it vlan trunkING protocol or vlan trunk protocol?

I’ve seen both terms used. When I renewed my CCNA in 2006, I had a CCSI tell me specifically that is was VLAN TRUNK protocol. He emphasized that point a few times.

As I’ve started working through the BCMSN study materials and the CCIE Routing and Switching Exam Cert Guide, I’m seeing VLAN TRUNKING protocol. So which is it?

Here are two links with an argument for either side…