Sentence:  ... I hold a Prince ought not wholly to neglect Military Affairs, but verse himself in, and accustome himself to them, that he may <WSD>intonate</WSD> fear into Neighbours ... 
Meaning of the word marked with <WSD> tags:  To thunder or to utter in a sonorous or thunderous voice.<ref>"Oxford English Dictionary", 2nd ed., 1989.</ref><ref>"An American Dictionary of the English Language", by Noah Webster, 1828.</ref><ref>(Nathan Bailey), "Universal Etymological Dictionary", London: T. Cox, 1736, 2nd edition: I<small>NTONATE</small>, to thunder or make a rumbling noise.</ref>