Way back in the late 1970's I was serving on a trials team and temporarily stationed at Aberport in west Wales. During the time I was there it was my wedding anniversary and my wife arrived so that we could go out for a meal to celebrate. We decided to eat at a local pub (good food and good beer) and when we arrived the conversation in the room just stopped until we had sat down and started viewing the menu. From that point on everyone in the pub spoke Welsh exclusively and during the meal I sensed that my wife was a little distracted by a couple on a nearby table. At the end of our meal we paid and made to leave, at which point my wife turned to the woman on the table and spoke to her in perfect Welsh saying (something to the effect of) if you're going to slag off the English make sure the bu99erz can't understand you first
SWMBO had lived with an aunt for a few years and went to school in Caernarfon where they spoke Welsh exclusively. She used to curse me in Welsh too so I wouldn't know what she'd said/called me