In "The Bird with a Broken Wing," part of Agatha Christie's story collection, The Mysterious Mr Quin, Inspector Winkfield tells Mr Satterthwaite:
Must find out what terms they were on. That’s where you can be useful to us, Mr Satterthwaite. You’ve the ongtray here, and you can get the hang of things in a way we can’t. Find out what relations there were between the two.
What does "ongtray" mean? Searches on Google mostly yield the same quoted text, with people complaining that searching didn't yield anything useful.