HDL

Etymology

An initialism for "high-density lipoprotein," named for its physical density in the lab, where such particles are separated by how heavy they are. The density comes from a high ratio of protein to fat — more protein, denser particle.

noun · /aych-dee-EL/
High-density lipoprotein, the particle that carries cholesterol away from tissues to the liver for disposal.
What it names
The "good" carrier in a blood test — the one you want high — clearing up the myth that cholesterol is simply bad.
Example
His total cholesterol looked high until the doctor noted that most of it was HDL, which changed the picture entirely.
Related idea
HDL ferries cholesterol out of the arteries toward disposal, while LDL delivers it to tissues and, in excess, deposits it in artery walls — which is why one is nicknamed "good" and the other "bad," though both are needed.