The '12 o'clock joke' or 'Sardarji joke' refers to a class of jokes that stereotype Sikhs as being unintelligent or lacking common sense, with the implication that they are only 'in their senses' at midnight or 12 o'clock. However, the origin of this joke has a historical context rooted in the bravery and humanitarian efforts of the Sikhs.
The real origin traces back to the invasions of India by the Persian ruler Nadir Shah in 1739. After plundering Delhi, Nadir Shah's army was carrying away a large number of captured Hindu women as they retreated. The Sikh army, though outnumbered, launched daring midnight guerrilla raids on Nadir Shah's camps to rescue these captive women and restore their dignity. This became a routine practice for the Sikhs to launch such rescue missions at midnight when the enemy's guard was down.
As a result, people started saying that at precisely 12 o'clock (midnight), it was dangerous to confront the Sikhs, as they became extraordinarily fierce and powerful in their determination to defend the defenseless. This eventually led to the phrase "at 12 o'clock, Sikhs go out of their senses" being used, which over time morphed into the derogatory '12 o'clock joke' mocking Sikhs' intelligence.