That’s a good one - related, but not etymologically !
(afaik)
We have? I must have missed that, although I’ve looked over the thread a couple times. @Q.Q.Switcheroo did provide another 6-letter one: symptomatology, which is a very nice example. I don’t think there are any longer ones that satisfy my additional rules.
Nice! It satisfies the OP’s original post - eudemon and monism being unrelated - but does violate the OP’s revised condition that there must be letters removed on both ends. But even just eudemonistically is a winner at 10 out of 16, I’d say.
I wrote a Python script that looks for shorter words of a set length that exist inside longer words, filtering out pairs that start the same or end the same. Then I went through the output manually, looking at the shorter words for ones that don’t usually exist as elements in longer words. I ran it on the Moby Pronunciator word list (which doesn’t include inflected forms). When I limited the shorter words to exactly eight letters, nothing jumped out at me; I may have missed some. I haven’t tried looking for words longer than eight letters. For seven letters, I found more than I expected:
amphora inside camphorate (to treat with camphor)
another inside both organotherapy (treatment with extracts of animal glands) and galvanothermy (heat produced by electric currents)
chipper inside schipperke (Dutch dog breed)
dertrum (tip of a bird’s upper bill) inside undertrump (as in card games)
ovarian inside covariant
percale (a kind of fabric) inside supercalender (machine for treating paper)
rachial (relating to the spinal column) inside brachialgia (arm pain)
rummage inside brummagem (meaning “spurious”, derived from “Birmingham”)
rundlet (small barrel) inside trundletail (dog with a curved tail)
stamina inside histaminase (an enzyme)
venturi inside adventurism
winglet inside swingletree (alternate form of singletree, as of a wagon)
Doubtful cases:
ortolan (a kind of bird) inside portolano (alternate spelling of portolan=“navigation chart”). Depends on whether -o counts as a suffix.
hoeshin (supposedly a Scottish term for gaiters or leggings) inside shoeshine. Depends on whether hoeshin is a real word. I didn’t find it in the dictionaries I checked but there are some references to the word online and on Google Books.
pistole (old Spanish coin) inside epistoler (writer of epistles). Depends on whether -r counts a suffix (I guess it would if the word were epistler).
Most excellent results @bibliophage. As far as the doubtful cases, I think I’d be inclined to accept portolano but reject epistoler. As for shoeshine, reject that too unless someone can find hoeshin in an English-language dictionary. It’s not in Web3, but I don’t have Web2 handy.
Yes, this one is good.
This is a bit of a cheat, but I believe it fits the rules as specified: ecologist within gynecologists
Also: sumptuous in presumptuousness. The “pre” is not a prefix here; it comes from the difference between praesumere and sumptus in Latin.
It may fit the rules, but I think the most interesting ones are where no parts of the overlapping words mean the same.
Agreed, but I wasn’t able to do better than 7 letters without a shared suffix. If nothing else, it’ll force the OP to modify the rules again 
.
Exactly. How about reject any where suffixes and prefixes are shared between the two words, as well as root words.
I couldn’t think of a way to do it to get only the interesting ones. But perhaps the above modification will do the trick.
Another cheaty one: limitations.
No computers used, mind.
j