The Browns brother and sisters act, whose song you referenced The Old Lamplighter, had strong Christian roots and often sang of faith and family.
Being a Christian myself, I can't but suspect their reference to light in this song would likely have been double entendre for usage of lamps and light in the Bible.
Psalm 119:105: "Your word is a lamp to my feet and a light to my path."
Matthew 5:14-16: "You are the light of the world. A city set on a hill cannot be hidden. Nor do people light a lamp and put it under a basket, but on a stand, and it gives light to all in the house. In the same way, let your light shine before others, so that they may see your good works and give glory to your Father who is in heaven."
They would have seen the concept of "lighting the way for others" as symbolic since they came from a Christian background.
The concept of Christianity being light in a dark world has a great deal of historical cultural significance for Christians.
There are those who believe that "light" is what attracts so much attention and hatred.
btw...for those who put more stock into things quoted from Jesus, He also said,
Matthew 5:13: "You are the salt of the earth."
