Black Friday（n.）
popular name for the day after the U.S. Thanksgiving holiday (which always is a Thursday), in modern times the day which opens the Christmas shopping season and thus for stores often the busiest and biggest sales day of the year, but the exact sense of black (adj.) in it is uncertain.
It is attested by 1970 (in Philadelphia newspaper columns), said to be perhaps a merchants' term and a reference to the black ink that records profits. But the early articles also credit the expression to those who had the job of managing the crowds.
At 12th and Market, Traffic Patrolman Stanley Makarewicz took enough time out from conducting his orchestra of exhaust pipes to explain why policemen and cab drivers call it Black Friday.
"It's supposed to be worst day for traffic out of the whole year," the patrolman observed.
["Black Friday: Stores' Best Day," Philadelphia Inquirer, Nov. 28, 1970]
Earlier Black Friday had been used principally of Fridays when financial markets crashed (1866, 1869, 1873, 1929), the Kennedy assassination (1963) and other dark events.
该词起源时间：1970年