Posted by Grant Richardson, 25th May, 2015
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”.
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.