Reg Grundies
REJ GRUN-deez · rhyming slang
Undies.
Person 1"Forgot to pack anything?"
Person 2"Me Reg Grundies."
You'll also hear
Reginaldsshort version
Reggiesshort version
Where it's from
Rhyming slang after Reg Grundy, the TV producer behind Neighbours.

Something wrong or missing? Suggest a fix
While you're here
What's the story? What's happening, or what's the news?
The missus. Your wife or partner.
Head.
A look. Usually shortened to "a butcher's". In older Australian slang, being "butcher's" also meant being crook (sick).
Go for a piss.
Off for a turd.