One could do much better with the Oxford English Dictionary or other source which gives sources and complete definitions.

Yaffle is defined as the green woodpecker, but the word usage, mostly applied to its call, is pretty much confined to the region of Kent and surrounds. Much more common in the UK is its use to mean a bark, or a yelp; e. g., 1836 in Fraser's Magazine, "My faithful dog sent up a loud 'yaffle.'" Also used to mean to mumble, to talk indistinctly.

Y-front is a registered trademark of Jockey, a type of underwear common in North America, but usually called briefs (or hip briefs if abbreviated) there. The 'dictionary' defines y-fronts as pants (wrong unless called underpants), but the alternate definition of 'nut-choker' is descriptive.

Yarbles is defined as 'balls,' but one must look under 'balls' to find the definition of testicles. No indication of origin- it appeared in the Anthony Burgess book and film "A Clockwork Orange" and has entered urban slang in North America as well as UK.
A UK heavy metal group has taken the name.

WRM also is a Microsoft trademark (Windows Rights Management) and acronym for several other groups or things; wrm (as defined) appears as one of those stupid contractions in email, etc. in North America and elsewhere.