Why is the "Pretérito perfecto simple" also called "Pretérito indefinido"?

Question

As this answer points out, Pretérito perfecto simple and Pretérito indefinido refer to the same tense. This is actually quite confusing to me, because this tense is used for actions in the past that happened at a particular (=definite) time while Pretérito imperfecto, in contrast, is used when an action is not restricted to a specific time.

Ayer llovió. (Yesterday it rained.)
Cuando era niño iba a la escuela. (When I was a child, I went to school.)

In the first sentence, there's a particular time given (yesterday). It's definite when the action happened. In the latter sentence, however, there's just a vague time frame given (being a child) and that I used to go to school (=often, regularly) at that time.

My confusion's got solidified when I read this article. This article explains when you should use which past tense. And they say:

Another way to distinguish the two verb forms is to think of preterite as definite and the imperfect as indefinite.

So, this source actually confirms that Pretérito perfecto simple is considered definite and Pretérito imperfecto is considered indefinite.

Thus, why is Pretérito indefinido referring to the definite past tense?

Answer 1

“Indefinido” in this case is meant to be the translation of Greek “aoristos”, which means “undefined, unlimited, indeterminate”, and is a verbal tense in Ancient Greek. RAE chose it to highlight the contrast between that verbal tense and its compound counterpart.

It wasn't a fortunate naming, and in 1973 they changed it to “pretérito perfecto simple”.

Everything you wanted to know about “pretérito indefinido” and “aorist”: http://www.hispanoteca.eu/Foro/ARCHIVO-Foro/Indefinido%20y%20aoristo.htm

Answer 2

When I learned grammar at school (ca. 1983) they used two different naming systems for the verbal tenses. They were called "Spanish" (as from Spain) and "Andrés Bello" (in reference to the 19th century scholar who described it).

For the indicative mood, the tenses were:

Simple tenses

• Presente simple (S) = Presente (AB): camino
• Pretérito indefinido (S) = Pasado (AB): caminé
• Pretérito imperfecto (S) = Pretérito (AB): caminaba
• Futuro imperfecto (S) = Futuro (AB): caminaré

Composite tenses

• Pretérito perfecto (S) = Antepresente (AB): he caminado
• Pretérito anterior (S) = Antepasado (AB): hube caminado
• Pretérito pluscuamperfecto (S) = Antepretérito (AB): había caminado
• Futuro perfecto (S) = Antefuturo (AB): habré caminado

According to the reference by Angus, the RAE made the change in 1973, however it had not permeated the Colombian school system by 1983.

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I have noticed that in some places, particularly in Spain, the (composite) perfect past «he caminado» is used in most places I would use the simple (perfect) past «caminé». There is very little semantic difference between both constructions, particularly when used in positive sentences with indefinite time frame.

Caminé tres kilómetros. -- I walked two miles.

He caminado tres kilómetros. -- I've walked two miles.

(For me, when used with a definite time frame, the composite sentence sounds too European Spanish.)

Al medio día comí pasta. -- At noon, I ate pasta.

Al medio día he comido pasta. -- At noon, I've eaten pasta.

However in the negative, there is a significant difference:

No me comí la ensalda. -- I didn't eat the salad.

No me he comido la ensalada. -- I haven't eaten the salad.

The simple tense with the negative implies that the act of not eating salad is done: I stopped eating my lunch and I left the salad (and won't eat it later).

The composite, on the other hand, means that the act of eating the salad is not 'perfected' (negation of the perfect) yet. I haven't finished eating my lunch and so far I have not eaten the salad but I may still do it.

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In those three examples the imperfect has a completely different sense:

Caminaba tres kilómetros.

Depending on context, it means that I used to walk a couple of miles or that during a time frame defined by me walking the two miles something else happened.

Al medio día comía pasta.

I'm beginning to tell a story and I set the scenario: It was noon and I was eating pasta.

No me comía la ensalada.

This is also the setting for a story-telling.