Vroom...I did more of a proof of concept than any kind of search (being at work at all), but I have some bad news for you. I recognized a few of those off your list as being from ME books. I thought it may have been just some of the 2nd Ed. books that might have been missed by HotH (from being in the pipeline at the same time), but I'm afraid it isn't that simple. A few quick examples:
Klandun -> in Court of Ardor, don't know if it originated there.
Bragolith -> crap, I forgot already
...it was a poison somewhere...maybe the big Arnor book?
Chap Beech Nut -> has been in the Mirkwood sourcebooks since 'Southern Mirkwood'.
Numenelos -> is in Northern Wastes...but I don't think it originated there.
Sarah-P-H-Head -> 'Sarah pokes her Head', Mirkwood from 'Southern Mirkwood' on.
Waters of Fire -> acidic water from hot springs, in Arnor (big book), but don't know if it originated there.
As comprehensive has HotH seems, it appears it isn't (though an excellent sourcebook none the less).
A couple others that are tickling my memory, but I couldn't find them on a quick trip down memory lane were:
Mu-jy-Mirenna -> I thought this was in Ardor...it may be in one of the other Southern Midle Earth sourcebooks/modules (the 'mu-jy' looks very much like it is derived from one of the southern ME modules) . Seems like it was perhaps a berry that looked like a Mirenna berry, but with some sort of negative effect.
Wight Orchid -> also very familiar...seems like it was a plot device, but I'm not remembering any details.
I might be able to give it a go on a day off if you don't have access to the whole MERP library.
Jason