Webster's Revised Unabridged Dictionary · 1913

Water gall

Water gall

1.
A cavity made in the earth by a torrent of water; a washout.
2.
A watery appearance in the sky, accompanying the rainbow; a secondary or broken rainbow.
These water galls, in her dim element, Foretell new storms to those already spent. — Shakespeare
False good news are [is] always produced by true good, like the water gall by the rainbow. — Walpole