Parasara Muni said:
O Maitreya, the word Bhagavan is used to address the pure Supreme Lord, the cause of all causes, Who us named Mahavibhuti (possessor of great powers).
O sage, the syllable bha has two meanings:
Maintainer, and protector.
The syllable ga means:
Leader, carrier and creator
Bhaga (combined together) means:
Full opulence, strength, fame, beauty, knowledge and renunciation.
The syllable va means:
All living beings dwell within Him, the Supreme Personalities of Godhead, whose svarupa has being previously proved, and he dwells within all of them and and is therefore imperishable.
(Visnu Purana 6.5.72-75)