Posted by Grant Richardson, 5th September, 2018
The correct phrase is “jot it down”.
“To jot down” is an English phrasal verb which means “to write a note”.
A common mispronunciation (particularly by Hong Kong Chinese) is “drop down” or “drop it down“.
Some correct examples:
This point is very important. I think you should jot it down.
Before you call her, you should jot down some notes about what you want to say.