Ultraman (Title)

Despite the fact they are called Ultras, not ever Ultra is called Ultraman. It is in fact a title reserved for a slect few.

Etymology
The word Ultraman is a compound word composed of syllabels, 'Ultra' and 'Man'. Ultra is a shortening and synonim of the word 'Ulitmate' while 'Man' may refer to his humanoid shape. The closest word in japanese is Chojin, 'Cho' meaning 'Super' and 'Jin' meaning 'Man'. Basically Ultraman is a superman of sorts, fitting since his race is far beyond humans in terms of both, lifespan, abilities and knowledge.

Earning the Name
The title Ultraman is given only to those who visit Earth, or at the very least protected mankind. In Ultraman Hikari Gaiden it was said by Ultraman King, that the name was given to him by humans and is not his real name. In fact many Ultras do not use their real names, but they are refered to by their titles. A prime example are Seven and Ultraman. In each universe the term is coined in some form or fashion by one of the main characters.

In recent media the word has been used as the name for all Ultras

Trivia

 * Despite the fact he has never gone to Earth, is known as Ultraman Zero and introduced himself as such.