Lyric discussion by Veillantif 

People should remember that "maketh" is archaic English for the SINGULAR third-person of "make," not the plural. It can therefore only refer to "murder," not "words. The modern English equivalent of the phrase is "The words that murder makes."

That should make it much easier to understand ("I've seen and done things I want to forget").

@Veillantif Well done, thank you.

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