Monty was named after a beautiful springer that my parents owned during my early years.
I decided that a dogs name should end in an 'ee' sound and not sound to like the others, in the household, so each late dog had to have a different second letter (Vowel) sound and the two next letters different also, so it was a matter of going through combinations until I reached something that appealed.
With the second cavalier I arrived at Dizzy, but chose Izzy. Monty being short for Montgomery, Izzy was short for Isambard (Kingdom Brunel). It caused a lot of confusion , as Izzy was a pretty boy , so people assumed he was a girl. One day had me in hysterics, because a person wanting my son to do a pc repair, left a message, saying that Izzy was calling. At the time, my Izzy was sitting watching me and i just couldn't stop laughing. The customer/friend was Asian and was called Izzy short for his Islamic name.
Joly, after the same process was after Jolyon, in the Forsyte Saga .
Teddy needed a name short for something aristocratic, but he stared at me from a photo with his litter mates and the name Teddy , short for Edward, came into my head, so he picked his own name. Oddly, just as i decided, someone, on a forum pm'd me and suggested exactly the same, after seeing the photo.