I wanted to log in to the wiki to help a little bit with the editing of the pages, but I failed to register because of the captcha. The question is "what is tidal short for?".
Could someone please help me answering this question because I have no idea 
It's: tidalcycles
It started off as Tidal (well iirc, first diesel (as an expansion of DSL/domain specific language), then the next version was petrol, then tidal, then smooth and then tidal again). Then some streaming service started up with the same name so we decided to call it tidalcycles to differentiate it from that.
Well, I did not expect that now 
And many thanks for detailed explanation. I will give the wiki registration a new try now!
[Edit:] As expected, I have now successfully registered.