Hi Kat,
sorry pardon, Matelot (pron Mat-low) isn't actually slang although its use is probably restricted to the Navy these days. It's a lower deck member of the RN as opposed to the Merchant service.
Pongo = RN slang for a member of the Army (from the latin name for the species commonly known as the orangoutang.)
Since someone has asked in another thread about Grey funnel line, Grey funnel line = The Andrew = the RN.
Talking of things not being explained you have mentioned a could or so times Kat that you write an "op ed" column. What's one of them when they're at home?
Pete M