Cocks, hens and babalwbi

If you emerged from a mystery tour to see these  quartz-topped walls and gate pillars all around you could be sure you were in north Pembrokeshire.
It's an old custom  here to use lumps of quartz to decorate the stonework around  cottages and houses, particularly along the road like this.  Efforts are made to preserve the tradition and the original boulders are often reset, as here. It's a piece of  vernacular architecture that makes this area special but no one seems to know its  the significance,  if any.
However, white quartz has been considered slightly mystical the world over and often associated with, or incorporated in, prehistoric  structures.*
Many of these solid stones houses were built by mariners upon their retirement: this one is a typical 'captain's house'. They would have made a bit of money and wanted to show off - and the ornamentation  catches the eye.  

Another possibility:  in the days before street lights did the luminescent coping simply help to guide folk home on dark nights?

Cock and hen coping is the name for the technique of alternating vertical and horizontal  stones along the top of a wall  and it's sometimes applied to pair of stone gateposts similarly contrasted at the top. (I guess no one needed to look far for the reason.)

But somewhere, once,  I came upon the information that the quartz excrescences were called babalwbi (babaloobi). I love the word but can find no explanation or confirmation. If I google it I discover - myself!

Any ideas? Postscript: see here for more about the above.

*As for example at the nearby  Trefael stone where a line of quartz boulders were uncovered in a trench http://www.archaeology.co.uk/articles/features/trefael-the-dolmen-that-became-a-standing-stone.htm