Whence cometh the name....
It was common for people, women especially, in the 16th century to be called "spitfires" after a foot-stamping display of visciousness and bad temper.
Shakespeare, 500 years ago, in King Lear (Act 3 Scene 2) had the King exhorting: 'Rumble thy bellyful! Spit fire, spout rain!'
My father even used this name for a little girl he knew well, who would occasionally put on a good show of petulance,
...and the Chairman of Vickers, who had previously purchased the Supermarine company (which had just designed a new fighter aircraft) thought he'd name this aeroplane after his daughter Anna's playacting - apparently she was "a right little spitfire....."
So I thought that if a water (and especially effluent) irrigating machine that spat venomous, foul material from its mouth was also named a "Spitfire" then it was a rather apt appellation.
Now you know.