So a little background; first time I saw this video, a buddy of mine posted it..  We're both from outside of Boston, so it's not everyday we see some true Welsh jargon..  Regardless, dude in the video pulls off what I believe to be one of the sickest freestyles in all of rapping, however it turns out that it's just the name of a town in Wales..  Good god..  How do you guys remember that kinda stuff??  Perhaps WE'RE the cavemen?!  lol  Our towns here in New England are similar to a lot of UK towns/cities, however, we don't have this..
I'll caveat that with the mention of a lake that we have here..  Most locals call it Webster Lake but it's true name is Lake Chaubunagungamaug, which is alleged to mean, "You fish on your side, I fish on my side and no one fish in the middle"..  I imagine the Welsh town is similar in meaning??   Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch?  (Just added it to 'Spell Check')