Why are S and Z treated differently by the rules for stress?

Question

Unless an accent is present, the stress falls on the second to last syllable when a word ends in a vowel, N, or S. But Z seems to "want" to follow this rule as well. In almost every name ending in a Z the stress is moved to the second to last syllable by an accent. The same pattern seems to show up a lot in common nouns. Since this is the case, why didn't the Royal Academy expand the stress rules to include Z alongside S and N?

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A menos que haya una tilde presente, el acento recae en la penúltima sílaba cuando una palabra termina en vocal, N o S. Pero parece como si Z "quisiera" seguir esta regla también. Casi todos los nombres que terminan en Z mueven el acento a la penúltima sílaba mediante una tilde. El mismo patrón parece darse mucho en nombres comunes. Siendo este el caso, ¿por qué la Real Academia no amplió las reglas de acentuación para incluir la Z junto con la S y la N?

Answer 1

While many surnames ending in -ez are stressed on the second to last syllable, most words ending in z are stressed on the last. Many of those words come from applying the suffix -ez to a noun to form an adjective:

redondo → redondez
estúpido → estupidez

..etc. But, in general, not even counting them, there are more words ending in z stressed on the last syllable than otherwise (off the top of my head, I can only think of lápiz and pómez).

The rule makes sense, because it minimizes the amount of words needing a written accent.

Answer 2

Orthographic rules are historical conventions accreted over time and they're not always optimized.

In Spanish the rule treats penultimate-stressed words (palabras graves) as the default, so they don't need an ortographical accent, unless they end in a consonant, except s or n. Why? In terms of optimization (least number of accents), it makes sense because most nouns form their plurals in -s and finite verb forms always end in a vowel, or -n, or -s.

But in historical terms, these two final consonants (serving those functions) descend from Latin forms where the stress was, as today, often on the penultimate syllable. This is in contrast with, for example, the verb infinitives, which in Vulgar Latin ended in -áre, -ére, -íre, so that when the final -e was lost the stress pattern shifted (from grave to agudo). The same thing ocurred with many other words now ending in consonants other than -s and -n: the original Latin usually was penult-stressed and lost its ending (vowel + optional consonant).

It seems that for most words the origin of modern -z is generally a Vulgar Latin ending -cis for adjectives (which is the accusative ending for adjectives ending in -x), and, for the common noun-forming suffix -ez, the Latin -átis. These were always penult-stressed: capácis, velócis, procácis, naríces or narícem, stupiditátis. When the final syllable was eroded and lost, these all kept the stress on the same syllable and so predictably shifted from graves to agudas. So it "made sense" to stipulate that final -z moved the stress with it, I guess.

You can test this idea by looking at the etymologies of the Spanish words ending in z.

Answer 3

Most of the z-ending names you are probably thinking of, are surnames ending in -ez.

Many patronymic surnames in Spain have been formed by adding the -ez suffix to a name, and these surnames have retained the accent in the same syllabe than the original names. For example:

• Martín -> Mart'in -> Mart'in-ez -> Martínez
• Sancho -> S'ancho -> S'anch-ez -> Sánchez
• Hernándo -> Hern'ando -> Hern'and(o)-ez -> Hernández
• Gonzalo -> Gonz'alo -> Gonz'al(o)-ez -> González

So it is not that z-ending words want to be second-to-last accented, it's just that most z-ending surnames are pronounced like that because of the name they come from.

And regarding your impression that this happens a lot in common names... Well: of the 488 z-ending words linked in pablodf76's answer, only 15 of them are common words (not surnames) which have an ortographic accent at all, so not exactly common. (The list itself is very questionable, but it serves as an example.)