I came across this phrase in The Valley of Fear, one of The Greatest Adventures of Sherlock Holmes. However, the reason it caught my attention is because I believe the phrase is used in a song in Les Miserables. I think I’ve been singing it wrong for a very long time! It makes a lot more sense now.
Boon – jolly, jovial, convivial; something to be thankful for
Therefore, a Boon Companion is a fun person to be around, someone you would be lucky to know. And that is what people thought of John McMurdo in The Valley of Fear.
Usage: “He was a born boon companion, with a magnetism which drew good humour from all around him.”