Thanks to Dh, it is now possible to add etymologies in Omegawiki (in fact, since about a month).
It has been implemented as a translatable text attribute. It means that the etymologies for any word can be explained in all languages.
This may seem like an overkill, and actually, the initial idea was to have only one text field, and to enter the etymology of a word in the language of that word, since we expected that only people who know a language would be interested in etymologies of words of that language.
However, while I might be interested in the etymology of a Latin word, I am not able to write it in Latin, and there is also no particular reason to write it only in English in that case.
What is missing now is the possibility to have etymons as links to the corresponding DefinedMeanings. This is also a desired feature for having the words of a definition linking to the corresponding DM to avoid ambiguity, and will need further development.
Have fun adding etymologies,