Green’s Dictionary of Slang

secret, secretive.

1997–2000		College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 DL (down low) (d/o) (adj.) Down low; secret.
2000		Ebonics Primer at www.dolemite.com 🌐 down low (also D-L) Definition: subversive, so no one will know. Example: The cops is after me, so’s I got to keep my shit on the down low.
2022		J. Hannaham Didn’t Nobody Give a Shit 73: He really ain’t rised above the kind of mentality a them DL rapist thugs that's up in Ithaca.