These are good examples of what linguists call a "Volksetymologie", meaning a usually wrong derivation of words which are no longer correctly understood or have changed meaning. A popular example is when a German newspaper did one of those stupid surveys for the "most beautiful German word", and the winner was "Habseligkeiten". The cited reason was because it combines "Haben" (to have) with "Selig" ("blessed"), the profane with the heavenly, but the real etymology is actually different.
As is already mentioned here, the "-mut" in Wehmut does not mean "courage" but is actually identical to the English "mood". I would also highly doubt his interpretation of "Einsam". The suffix "-sam" usually means simply to having something. "Liebenswürdig" is difficult, because "Liebe" means many things (from simply "friendly" to modern romantic "love"), and "-würdig" is more in terms of being adequate or appropriate. When you say "Er ist sehr liebenswürdig", this does not mean that HE is worthy of love, but simply that he is a friendly person, meaning he knows how to treat people properly. As was also already mentioned here, "Entwicklung" and "development" are literally the same, and the same goes for "Ursprung" and "origin".
There is also the simple fact that German allows for building compositions, so what would be considered an expression in English can be one word in German (like "Sinneswandel" for "change of mind"). But this does not mean that it "does not exist".
As a German, the word I'm really missing when speaking English is the simple word "doch", which more or less means "No, but yeah". If you've ever watched German kids in a "Nein! Doch!" match, you know how powerful that simple word is. I think there was actually an article here some time ago that English used to have this with "Yay" and "Nay" in addition to "Yes" and "No", but that this got lost. Of course German is not unique in having "doch", most other roman languages have it as well (the French have "Si", which in Italy is the normal "Yes").
EDIT: Found the article:
https://www.newyorker.com/books/page-turner/what-part-of-no-...