On the down-low, or on the DL, refers to information that's kept quiet or under wraps. It emerges in Black slang by the 1990s. Both down and low underscore the slang's sense of “quiet” and “hushed.” Since at least the early 2000s, down-low refers to men who secretly have sex (on the down low) with other men.

What does drop it down low mean?

It's "slang" for basically having a woman get low while dancing.

What does get the lowdown mean?

: important information or facts about something He gave me the lowdown about the company's vice president. Reporters are trying to get the lowdown on what caused the accident.