Mamie, funny but for me 'trou en formation' takes another meaning (as a native French speaker) 'en formation' means 'in training' ... so I always think they are learning how to be better and bigger holes (bigger they do become...).
I love the French 'proverb' seen by railway crossings : un train peut en cacher un autre' - one train can hide another (eg don't think it is safe to cross because one train has passed, another may be right behind) - it could apply to so many things, jobs, boyfriends, etc.
For me, as said before, 'puke' was a new word - and Pukka just seemed like that word with a (French) past tense ending. I know now that the 2 'ks' give it a different meaning, but not at the time, as a freshly arrived immigrant in the UK.