turismo

This looks like the tidiest pair in the language and it is not a pair at all. Esperanto has a real suffix -ism- for doctrines and systems, and a real suffix -ist- for the people who hold them or practise them. Komuna common gives komunismo and komunisto. Esperanto gives Esperantismo and esperantisto. So turismo and turisto look like the same machine running on a root tur-, and a learner reasonably asks what tur- means.

It means nothing, and the dictionary says so twice. The Esperanto dictionaries list turism/o and turist/o as two separate roots, each borrowed whole from French. Neither is built from the other and neither is built from anything. The proof is quiet but total: turism/o has its own verb, turismi, to travel for pleasure, which could not exist if -ism- were the abstract suffix doing suffix work. You cannot verb a doctrine that way.

And the one root that does start tur- is a red herring. A turo is a tower. On the suffix reading a turisto would be a tower-keeper, which is a much better word than this one and belongs to a different language. The turisto page makes the same point from the other end, and the two pages together are the clearest illustration in this band of a rule worth carrying: a suffix only counts as a suffix when the root it leaves behind is a word.

The related class. Barbaro at 2,135 catches people the same way, looking like barb- plus a collective; it is one root. Organismo is not an organ plus a doctrine. Turnisto is not a word. Vojaĝanto, from vojaĝi, really is built by rule and means a traveller in the neutral sense, without the camera.