I live near Seattle, which has nicknamed itself The Emerald City. A school of Irish dance calls its performing troupe The Ballyglass Dancers, Bally being the way the Irish "baile" (home, town [baile mór]) is often rendered when place names are Anglicized, and "-glass" being the Anglicization of glas. I think it kind of cute.
In Welsh, glas means blue! They are both Celtic languages and as far as I can tell glas used to mean a blue-green, with no distinction between green and blue. This is common in many languages, and only in modern times do languages begin to discriminate (http://www.sciencealert.com/humans-couldn-t-even-see-the-colour-blue-until-modern-times-research-suggests). It seems that with the same word Welsh took one path and Irish took another. I often wondered as a child that it was strange that some colours were (it seemed to me) definite, like red, and others came in many shades, like blue and green. What I mean is, a light red is pink, a darn red is maroon, a yellow red is orange etc. Whereas blue and green can be described as dark or light without having another word to describe them.