>>46131
>>46138
It's a common peasant bird and the sound evokes rural nostalgia for many. Most probably don't think in terms of species but are still aware of its significant differences in taste and behavior from regular chicken.
Tô-fraco is a biased interpretation because it also means "I'm weak" and onomatopoeia directly corresponding to real sentences seem to be more effective in becoming the standard, even when they're not the closest to the real sound. A famous example is the bem-te-vi:
https://youtube.com/watch?v=07LWGUcKs18 [Embed]

But no way it's csirp-csirp. There are a lot of othe ways to word it besides tô-fraco, but in any case you need at least two vowels.