interjection
ahem
uh-HEM/əˈhem/
A throat-clearing sound used to discreetly draw attention.
“Ahem,” the customer says with a throat-clearing sound to attract the distracted attendant's attention.

Etymology
Hem imitates clearing the throat as if preparing to speak. Ahem extends that sound into an interjection used to draw someone's attention.
In context
Ahem. So it turns out, in this whole room, I'm the only one out of the loop.
More examples
- Ahem, may I ask a question?
- Ahem, you seem to have forgotten your change.
- Ahem, someone is waiting to speak to you.
Similar words
- cough
- Usually names a reflex clearing the throat or lungs.
- excuse me
- Directly requests attention or acknowledges an interruption.