“Etymology” literally means a study of ‘true things’ (Greek etyma), so the notion of a ‘false etymology’ is an oxymoron - a term that contains its own contradiction. I enjoy teasing out a good oxymoron, especially when they are almost clichés, such as ‘no comment’, ‘virtually unique’, and ‘deafening silence’. A French friend once told me that his favourite oxymoron was ‘English cuisine’, but that is outdated as food in good English restaurants now often outclasses that on the continent.
The best false etymologies are those that look so plausible that one has to think twice before rejecting them. How is it possible that ‘outrage’ is not derived from ‘out’ and ‘rage’? In fact it comes from the French ‘outre’ (‘beyond’) with the noun suffix -age (as in the dreaded word ‘outage’); if something is ‘outrageously good’ it is good beyond expectation. False etymologies can appear in the most common words: ‘have’ is not from Latin ‘habere’ but derives from a word related to Latin ‘capere’, hold (‘capture’), ‘time’ has no relation to ‘tempus’ or ‘temps’.
The late Colonel Gadaffi was said to have insisted that Shakespeare was of Arabic descent, and that his name was an Anglicised version of “Sheikh Zubeir”. It’s 1 April, so I have proposed a similar false etymology of “April Fool.” The Arabic 'ful' means a broad bean (fava), the best varieties of which were traditionally sown on 1 April (it is in fact true that broad beans are sown in spring). "April Ful" took on negative connotation after the term 'ful madammas' (stewed beans) was misheard as 'Fool, madam, ass!'
Have a good 1 April…
You gave me something to think about here - with “outrage”. I don’t dispute your explanation of the word’s origins, but in common usage it also means something like “intense anger”. I don’t think it is your intention to call this usage into question. That would be rather severe.