Literal Translation
To hold the candle
Actual Meaning
To be the third wheel
Etymology
Before electricity and bedside lamps, couples who wished to be able to see while in bed had a valet hold a candle, with his backed turned of course! This was particularly true for newlyweds. The meaning moved towards having to watch powerlessly because it was common to be jealous or in love with one’s employers. A somewhat lighter meaning appeared linked to chaperoning a young couple.