I think that this is the one you are referring to?

MOCHYN DU (BLACK PIG)

Redodd dito i Llwyncelyn,
Mofyn Matti at y mochyn,
Dwedodd Matti, o mor arw
Mochyn clysydd bron y marw.

Chorus:
O mor drwm yr ydym ni
O mor drwm yr ydym ni.
Y mae yma alar calon
Ar ol claddew mochyn du.

English translation is thus:

Run my David to Llwyncelyn
To fetch Mati to the piggie,
But Mati told us quickly,
That the black pig was dying.

Chorus:
Oh, our Hearts are very sore,
Oh, our hearts are very sore,
Oh, our hearts are very heavy,
When we buried the black pig.

This is a Welsh folk song of course, but it was very popular on ships that carried an entire Welsh crew, where it was used as a capstan shanty.

English words were sung to this tune as well. There are many versions including one with the ridiculous chorus line: "Was you ever saw, was you ever saw, was you ever saw such a funny thing before?"

I am afraid that I do not possess the full version of "Mochyn Du". But I can probably find itversion if I set my mind to it.

HTML line breaks added. --JoeClone, 2-Feb-02.