Sentence:  ... I have found a cure for his lunatic excellency. Water expelleth fire—marry, when he talks of being an archbishop, souse him, good Tio,—<WSD>fishify</WSD> him straight,—may be his madness is a dog madness which flieth from the fountain. 
Meaning of the word marked with <WSD> tags:  To make as wet as a fish; to drench with water.