Gourders of Rain

Will any of your correspondents be kind enough to suggest the etymology of the word "gourders" (= torrents)? It occurs in the following passage of *Harding against Jewel* (p. 189., Antv. 1565): "Let the *gourders* of raine come downe from you and all other heretikes, let the floudes of worldly rages thrust, let the windes of Sathan's temptations blowe their worst, this house shall not be overthrowen."