I tried that too, I called it "agents". (This was long before AI-mania.) An agent was an object that handled some aspect of behavior (like gravity and collision physics) "on behalf of" some entity, hence the name. The word I was actually searching for was probably "delegate", but I was a stupid 20-something.
ECS is to me still conceptually cleaner and easier to work with, if more tedious and boilerplate-y.
Traditionally called something like entity and attachments.