Sentence:  deprecating being taken for ſerious, or to be underſtood that he meaneth any thing by them; but only that he uſeth them as <WSD>expletive</WSD> phraſes ... to plump his ſpeech, and fill up ſentences. 
Meaning of the word marked with <WSD> tags:  Serving to fill up, merely for effect, otherwise redundant.