Why do we call a case a casus? And why rectus, obliquus?

Question

I would translate the grammatical word casus (whence English case) as "a fall". And, indeed, the German word is Fall, Dutch naamval ("name fall"). Why is this word used for the grammatical function of nouns?

The Romans already used casus thus. But its connotations were "occurrence" and "accident" (which happens to be cognate with case), which do not seem related in meaning at all to the grammatical sense.

There must be some kind of metaphor at work. During my studies, we were told to imagine the casus rectus (undeclined or nominative form) as a stick or line standing up straight, the obliquus as slanted at an angle. Indeed, the verb declino was also used by the Romans to mean "1. slant down; 2. decline grammatically". English inflect also fits.

I can understand this metaphor, but it seems somewhat odd. Why would a grammatical function be standing up?

In addition, it seems to conflict with casus as a metaphorical fall. A fall is downwards, and how does a slanted fall work—let alone a leaning ("declined") fall?

I believe there is a conexion between Greek κλίνω and declino, as the former is also used for grammatical declension. The same applies to ὀρθός "rectus" and πτῶσις "case", which apple the same mataphors. Is the Latin just a loan translation? In that case, how did Greek come up with falling and leaning at the same time?

Answer 1

Here's a short answer so far - no one knows.

Brandenburg 2013 writes that

"In non-technical contexts, ptôsis refers among other things to the ‘falling of dice’ (Pl. Resp. 10,604c6; Aristot. Eth. Eud. 9,1247a21-23). In the grammatical terminology it refers to the forms of nominal declension. This, however, renders the metaphor of falling unintelligible, because it is far from obvious in what sense the cases are falling and, if they do, where they are falling from. It is this question that has inspired a lively discussion among the different currents of ancient grammar."

or Thorp 1989:

"It seems likely that the language about verticality and obliquity was introduced, about a hundred years after Aristotle, by the Stoic scholar Chrysippus. One can only speculate about what he had in mind with this language. It may be that he hadn't very much in mind: even in antiquity he had the reputation of an absurdly prolific writer, and of one who was so full of things to say that he hadn't time to settle his technical language very carefully. If this is right, then Chrysippus did what that boy in my first day of Latin did: he pressed a metaphor. Moreover, he pressed it clumsily. And he started a lot of trouble.

See Brandenburg 2013 and Thorp 1989 for a thorough discussion why we can't answer this question.

Fragments from Chrysippus can be found here

A very useful dictionary entry πτῶσις in Montanari - note sense B. gramm. inflection, modification of a word, from which a word or a different form originates.

Answer 2

It appears that you are correct that a casus is seen as a kind of metaphor for a noun "falling into place."

Maurus Servius Honoratus (4-5th century AD) has an important quote that makes two points that bear on your question:

Casus plerique quattuor esse dicunt, auferentes nominativum et vocativum, qui similis est nominativo. ideo autem auferunt nominativum, quoniam, cum casus sit dictus ab eo, quod faciat nomen cadere, nominativus e contrario rectum nomen ostendit. (Honoratus, Commentarius in Artem Donati 433)

Many say that there are four cases, leaving out the nominative and vocative, which is similar to the nominative. The reason they leave out the nominative is that, because "case" is said from the fact that it makes a noun "fall," the nominative instead shows the noun "upright."

The unexpected point is that the casus rectus is often not seen as an actual casus.

This idea does not begin with Honoratus: Varro (116 - 27 BC) makes the same point in less explicit terms:

Propter eorum qui dicunt usum declinati casus, uti is qui de altero diceret, distinguere posset, cum vocaret, cum daret, cum accusaret, sic alia eiusdem modi discrimina, quae nos et Graecos ad declinandum duxerunt. Sine controversia sunt obliqui, qui nascuntur a recto: unde rectus an sit casus sunt qui quaerant. (Varro, Lingua Latina 8.6)

Cases are declared based on the use of those who are speaking, so that one who is speaking of another can distinguish when he is speaking, giving, accusing, or other distinctions of the same kind which have lead us and the Greeks to declining. The oblique [cases], which arise from the "upright" [case], are uncontroversial: but there are some who wonder whether the "upright" is actually a case.

Your specific questions about the imagery of "falling" and "slanting" are difficult to address individually, but here's a stab at making some sense of the process based on the above.

1. A noun has a "archetype" nominative form, called the rectus
2. Other forms are derived from this and hence are called obliqui, i.e. "indirect." I see no reason to assume a "slanted" imagery when "indirect" is a commonly accepted meaning of obliquus.
3. These derivations were seen as a kind of "falling" from the right form, hence casus
4. The term casus then began to apply to all forms indiscriminately.