To burn the midnight oil is to work late into the night. Burning the midnight oil, burn the midnight oil again, no more burning the midnight oil.
The oil is lamp oil, and the phrase is older than electric light by two centuries. To burn the midnight oil implies work rather than pleasure, so nobody says it about a party.
1phraseburn the midnight oilTo work late into the night.
“Students often burn the midnight oil in the week before their exams.”
burn the midnight oil is a working.
From burning lamp oil for light at night; the phrase midnight oil is attested from the mid seventeenth century.
Originally referring to the act of burning lamp oil in oil lamps for light at night. The collocation midnight oil is attested from mid 17
Etymology from Wiktionary, CC BY-SA
Practised in Idioms