the.com/candlepower

means A unit of luminous intensity originally defined as the light given off by one standard candle, now largely replaced by the candela but still tossed around informally to mean 'really bright.'

from Straightforward 19th-century compound of 'candle' plus 'power,' born when standardized wax or spermaceti candles burning at a fixed rate became the literal physical benchmark for measuring light intensity. Scientists needed a unit, and the humble candle — something everyone could picture guttering on a table — was the obvious ruler to hold up against gaslight and early electric bulbs. The term stuck around in everyday speech long after the candela quietly took over the technical definition.