Refers to the historical Japanese Imperial Guards, the military organization that protected the Emperor and the Imperial Palace.
The Imperial Guards were responsible for protecting the Emperor.
近衛 refers to the historical Japanese imperial guard as an institution, while 親衛 is a more general term for a ruler's personal guard used across contexts.
Compound of 近 (kon, 'close') and 衛 (ei, 'guard'), referring to guards who are close to the sovereign.