There is a children's song to it:

Dacw, dacw fuwch, ac arni gyrnau gleision,
Nid am y fuwch 'rwy' bron a^ thorri 'nghalon,
Ond am y ferch, lle roddais i fy serch,
A welais i yn ei godro.

Dacw, dacw stwc, ac arni gylchau gloywon
Nid am y stwc, 'rwy' bron a^ thorri 'nghalon, ...
Ond am y ferch, lle roddais i fy serch,
A welais i yn ei chario.

Dacw, dacw rw^m, a'i llond o lestri ddigon
Nid am y rw^m, 'rwy' bron a^ thorri 'nghalon ...
Ond am y ferch, lle roddais i fy serch,
A welais i'n eistedd yno.

Roughly:
There, there is a cow with blue horns
But it isn't for the cow that my heart is breaking
But for the girl to whom I gave my love
Who I saw milking it.

There, there is the pail with shiny rings,
Buy it isn'f for the pail that my heart is breaking
But for the girl to whom I gave my love
Who I saw carrying it.

There, there is the room full enough of dishes,
But it isn't for the room that my heart is breaking
But for the girl to whom I gave my love
Who I saw sitting there.

The tune is often used in a set with another - "Robin Ddiog" (Lazy Robin) - for a dance of that name.

Robin Ddiog
Double circle. Couples facing couples. Man with partner on his right. One couple facing clockwise; the other, counter clockwise.

1. Right hand star and left hand star.
2. First couple (facing clockwise) form a bridge and walk 4 paces ahead while second couple walk 4 paces ahead under bridge counter clockwise. Couples turn, couple two makes the bridge and one proceed under it. Turn again a third time but this time progress to meet couple from the next foursome.
3. Repeat

Pretty basic dance which probably has other names elsewhere. Standard twmpath dance for a) children b) clueless grown-ups.

sian