[Sundae]

SOS is pretty much all I know in Morse code.
I learnt it from John Wyndham's The Day of the Triffids, where Bill signals Josella across the countryside (it's the only Morse Code he knows too!)

The fun fact is John Wyndham's full name is John Wyndham Parkes Lucas Beynon Harris. That was in the days before names were taxed.

ETA I did have to look this up to make sure I had it exactly right (I had a mispelling and the order wrong in truth) but it was something I pretty much knew.