Mustn't grumble

This morning I thought I'd discovered a word new to me, which is always one of life's minor pleasures. I was checking on the latest symptoms of this tiresomely indefatigable cough of mine, and came across the medical term 'rales', describing one of the four diagnostic lung sounds. Naturally I assumed this was a good old English word, probably of obscure origin. So I was rather disappointed to discover that it is simply the French word 'râles', stripped of its circumflex and adopted into the English medical lexicon. 'Râle' essentially means rattle, as in the cheering 'râle de la mort' or 'râle d'agonie', but the verb 'râler' can mean, colloquially, to grumble or grouch. 
So, mustn't râler, it's not the râle de la mort...