The story
Originally a reference to one of Jesus Christ’s parables recorded in Matthew 5:14–15, Mark 4:21–25, and Luke 8:16–18 of the Bible. For example, in the King James Version the passage from Matthew states (spelling modernized): “Ye are the light of the world. A city that is set on a hill, cannot be hid. Neither do men light a candle, and put it under a bushel: but on a candlestick, and it giveth light unto all that are in the house. Let your light so shine before men, that they may see your good works, and glorify your father which is in heaven.” The parable uses the imagery of a candle hidden under an overturned bushel (“a dry-measure vessel with a capacity of eight gallons”), and is interpreted as a call to Christians to set a good example through their actions that other people may come to believe in the faith.
Etymology from Wiktionary, CC BY-SA 4.0.