Louro or loiro?
Louro and loiro (m) or loura and loira (f), from Latin laurus, refer to any blond person. Louro is also a common affectionate nickname for all sorts of parrots (a controversy is that it might stem from Maori nori or Karib roro, through Spanish), and also refers to the condimentary and medicinal bay leaf plant (cf. laurel), while loura/loira refers to a light beer (with loura/loira gelada, literally "iced blonde", being a common name for the drink in its ideal state), or to the pound sterling.
But how exactly did we get to those two forms? It stems from a phonological process in which Portuguese changed ou to oi in many words, so that we could keep the diphthong in pronunciation, instead of moving those to a monophthong (as is the case in Spanish).
Dous, cousa and doudo (from which the name of the Dodo bird comes from) are dated forms for dois (two), coisa (thing) and doido (crazy one), which you can find while reading a book by Machado de Assis in its original spelling.
You can use them in humorous speech, particularly if you are to poke fun at someone or something that comes across as backwards or aristocratic, but it is not standard anywhere and will sound affected, though I'm certain someone somewhere in Trás-os-Montes probably still speaks that way - after all, they still distinguish s/ss from c/ç, and s from z, in their speech, like we did about half a millennium ago. (Thus why sussuarana, another name for the onça-parda or cougar/mountain lion, entered Portuguese as çuçuarana, as the Tupi /s/ is best represented by the ç sound; we no longer use ç word-initially.)
In a similar fashion, many innovations with the same theme ou > oi are considered substandard. That is the case of loiça (crockery, slab), loisa (blackboard), coiro (leather), toiro (bull), oiro (gold), caloiro (freshman) and poiso (landing), if you talk that way, many people will think you are an illiterate or semi-literate person from the countryside, though many of those forms were once more common and accepted.
Loiro and louro (pronounced with the diphthong) are equally as prominent in standard Brazilian Portuguese (I think louro is particularly common in Portugal as well); you will usually hear louro in vernacular Brazilian Portuguese, but as the monophthong ("lôro").
Aside from those, toucinho and toicinho (bacon, lard) are also accepted and commonly heard in both forms, albeit there is a noticeable preference for toucinho in standard Brazilian Portuguese.
I'm from Northern Portugal and we blame the southern parts of the country for the transformation of "ou" to "oi".
I'm a proud defender of: "louça/couro/touro/ouro/pouso/dourado/estourar", the rest, thanks to the wonderful help from the southerners, have changed to oi: caloiro, coisa, etc...
I've always heard it as caloiro...
And now that I've remembered:
The surname: "Goucha" is pronounced like "Goicha", the reason why it's pronounced like "Goicha" comes from a weird European Portuguese evolution. Basically whenever you have "Ch/Lh/Nh" in a word, a process called diphthongization occurs and an "i" is pronounced before them.
- We pronounce "acho" like "aicho"
- We pronounce "coelho" like "coeilho"
- We pronounce "venham" like "veinham"
And the surname "goucha" is no exception so we get a weird "Gouicha" but since the diphthong "ou" is pronounced like "ô", we get "Gôicha" --> "Goicha" but it's still written like "Goucha".