In Latin, ⟨x⟩ stood for /ks/. I'm a native Portuguese speaker and nowadays in my language this letter can also have the sounds /gz/, /s/, /z/ and /ʃ/. It seems relatively straightforward for me that /ks/ > /s/ and /ks/ > /gz/ > /z/. But /ʃ/ seems like an outlier, how did it get there? I'm curious to know what path exactly it might have taken, like /kʃ/ > /ʃ/ or /ks/ > /s/ > /ʃ/ (maybe even something else entirely!), what factors might have contributed to it being one or the other, etc.

I apologize if this has been addressed before but I couldn't find much results through queries such as "how did x become a fricative" and similars.

  • 4
    Are you asking about the development of a sound, or the use of a letter? These are utterly different questions.
    – Colin Fine
    Sep 16, 2022 at 17:35

2 Answers 2


In order to answer your question, I am going to assume that you are asking about the historical development of Lat. ⟨x⟩ /ks/ > Ibero-Romance /ʃ/, and not about the orthography. As Colin Fine has pointed out in his comment, these are two different issues, but I am going to focus only on the first one, as I feel this is closer to what you want to know.

First of all, the change in question represents the regular development of Lat. x in Ibero-Romance languages. If you find a Portuguese (henceforth Port.) or Spanish (henceforth Sp.) word that contains the sequences /ks/ or /gz/, and they have a clear cognate in Latin, then you are most likely dealing with a learned borrowing.

Having said this, if we want to explain the evolution of Lat. x > /ʃ/ in Ibero-Romance, we should consider that in Latin ⟨x⟩ represents a consonant cluster /ks/. Now, a peculiar sound change happened during the development of Ibero-Romance: I am talking about the yodization of every syllable-final occlusive. In symbols, we have Lat. t /t/, c /k/ > Iber.-Rom. *i̯ /j/. To give you some examples of this change, consider words like Lat. octō > Iber.-Rom. *oi̯to > Sp. ocho, Port. oito 'eight', Lat. auricula > Vulg. Lat. *orecla > Iber.-Rom. *orei̯la > Sp. oreja, Port. orelha 'ear', etc.

As you can see, this yod (by which I mean the * sound) has the power to palatalize almost any other sound coming before or after it, creating for example Sp. ⟨ch⟩ /ʧ/ and Port. ⟨lh⟩ /ʎ/.

So, what about Lat. x? Well, since this represents a cluster, as we've just said, we should expect a development like Lat. /ks/ > Iber.-Rom. *i̯s /js/, which clearly conforms to what has been discussed above. Then, this sequence *-i̯s- became /ʃ/ through the palatalization triggered by the yod.

A compelling example of this development can be found in Lat. coxā /koksaː/ > Iber.-Rom. *koi̯sa > Port. coxa /koʃa/ 'hip, thigh'. We have two pieces of evidence that allow us to claim that this is the right development. First, the Old Portuguese equivalent of coxa is coixa or coissa (a similar word coyxa exists in Old Galician as well). This confirms that in this word there was an old yod, occasionally written as ⟨i⟩ in Old Portuguese orthography. Secondly, Spanish has cuja 'a kind of bag tied to the hips of a horse', which is derived from the same Latin term. Normally, Latin o > Sp. ue, but in this case it undoubtedly developed into u because the starting point of the derivation was Iber.-Rom. *koi̯sa (with yod), and not *kosa (which would have given Sp. *cuesa). In fact, middle vowels in Ibero-Romance became high vowels in Spanish in the vicinity of a yod. Therefore, we have Iber.-Rom. *koi̯sa > *kui̯sa > *kuʃa > Sp. cuja.

All these elements prove that Lat. x /ks/ changed into *-i̯s- /-js-/ in Ibero-Romance languages. At a later stage, this cluster underwent palatalization, resulting in the expected outcome /ʃ/.

I hope this answers your question.

  • Thank you, this historical development is exactly what I wanted to know and it explains the orthography (that is, how ⟨x⟩ came to be associated with /ʃ/ in the first place).
    – Mutoh
    Sep 16, 2022 at 21:17

Despite the Latin precedent, the letter x was more-originally pronounced [x] in eastern Greek (not the dialect source for the Etruscan alphabet), and the name of the corresponding Greek letter (χ) is [çi]. That letter is widely used to represent a palatal fricative, especially on the Iberian peninsula. Therefore, there are two competing pronunciations of the letter x. In Portuguese, the older x-spelling was preserved, but Latin words were also borrowed, and the Latin pronunciation was retained, leading to some unpredictability in pronunciation of the letter.

The main historical puzzle, then, is what govern the choice of x vs. ch as the spelling of [ʃ] in Portuguese. It seems that the word xicara entered via Galician where x-spelling is regular. It may be that fricative x examples in Portuguese have such secondary sources.

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