Concise Bible Dictionary:

Strong’s Dictionary of Greek Words:

from 4172; a townsman
KJV Usage:

From Manners and Customs of the Bible:

Philippians. 4:8. With other my fellow laborers, whose names are in the book of life.
It was customary to have registers of citizenship, in which were entered the names of citizens, both natural and adopted. Heaven is represented as a city, and its inhabitants are registered. Some, who have not yet reached the heavenly city, are regarded as citizens on their way home. Their names are registered with the others. Such were the “fellow-laborers” to whom Paul refers in the text. See also Isaiah 4:33And it shall come to pass, that he that is left in Zion, and he that remaineth in Jerusalem, shall be called holy, even every one that is written among the living in Jerusalem: (Isaiah 4:3); Daniel 12:11And at that time shall Michael stand up, the great prince which standeth for the children of thy people: and there shall be a time of trouble, such as never was since there was a nation even to that same time: and at that time thy people shall be delivered, every one that shall be found written in the book. (Daniel 12:1); Luke 10:2020Notwithstanding in this rejoice not, that the spirits are subject unto you; but rather rejoice, because your names are written in heaven. (Luke 10:20); Revelation 13:8; 17:8; 20:15; 21:278And all that dwell upon the earth shall worship him, whose names are not written in the book of life of the Lamb slain from the foundation of the world. (Revelation 13:8)
8The beast that thou sawest was, and is not; and shall ascend out of the bottomless pit, and go into perdition: and they that dwell on the earth shall wonder, whose names were not written in the book of life from the foundation of the world, when they behold the beast that was, and is not, and yet is. (Revelation 17:8)
15And whosoever was not found written in the book of life was cast into the lake of fire. (Revelation 20:15)
27And there shall in no wise enter into it any thing that defileth, neither whatsoever worketh abomination, or maketh a lie: but they which are written in the Lamb's book of life. (Revelation 21:27)
. When one was deprived of citizenship his name was erased from the roll of citizens. Reference may be found to this in Exodus 32:3232Yet now, if thou wilt forgive their sin; and if not, blot me, I pray thee, out of thy book which thou hast written. (Exodus 32:32); Psalm 69:2828Let them be blotted out of the book of the living, and not be written with the righteous. (Psalm 69:28) and Revelation 3:55He that overcometh, the same shall be clothed in white raiment; and I will not blot out his name out of the book of life, but I will confess his name before my Father, and before his angels. (Revelation 3:5).