"However, mud in the sense of scandalous of defamatory charges goes back to a time well before the Civil War. In fact, this was an expression at least as long ago as 1846. So it seems most likely that the expression His name is mud was well established before Dr. Mudd met his unhappy fate."
"True. The OED lists a usage from early in the 19th century... and I wouldn't be surprised to find it had been used even earlier. The association of mud with worthlessness is obvious and natural."
This Q&A from an English professor is the best I can do, but he asserts it was current in USA as early as 1846, and that is when the German immigration was highest. No one has ever beaten me on these yet! Best, crystalk.
Which would have been a hot commodity in waterless Arabia! Where there's mud, there's water!
No doubt this incident would make a preexisting phrase popular. It would appear from a net search that the attribution to Dr. Samuel Mudd is universal, but that does not make it truth.
Your exercise in gematria that equates both to 98 is not convincing to me. How many letter combinations can produce the same result? If your answer is only two, your theory will gain great credence with me. I doubt this is the case.
My final feeling about this before I toddle off to a calling pillow:
If there is documentation that the phrase existed before 1865, then the phrase joins a long list of phrases that we use without knowing the true origin.
Play nice while I am gone :)
<shower>...