Where does the word "bravo" come from? In Spanish, it can be related to bravery but I fail to see the connection with the congratulatory mode it's used today in spectacles and related activities.
It comes from Italian (through French probably, but I'm not sure).
The original meaning was "brave, bold", as you could see in Spanish, but now it is usually taken to mean "well done!" or "good job". It still has the other meaning too, though.
The etymology is uncertain, it could come from Latin barbăru(m) ‘barbarian, savage’, or from prāvu(m) ‘pravo (don't know how to translate this), or evil’.
Think about "I promessi sposi" by Alessandro Manzoni, where you can see the so-called Bravi, a sort of soldiers under the commands of country gentlemen; they were one of the evil characters in the novel.
See also the Wiktionary entry for "bravo", it writes about both the meanings and usages, plus some other info.
There is something more on the etymology on this Italian Etymology Dictionary, but it's in Italian[*]. I'll link something more if I find it.
[*] The Italian Etymology Dictionary suggests various possible origins, from "bravus", probably a combination of the latinized Greek word "barbarus", i.e. a foreigner speaking a different language and "pravus": an evil person. Another possibility is "brabion": victory prize, and also a European root "bhrag" as in breaker of obstacles. Also note that the Italian word bravo comes from Latin ->Spanish ->Italian according to Treccani 6.