From Hull AWE
Some of the confusion that can surround the word case (see, for example, in case of - in the case of and the meanings listed at case) is because these four letters represent two words that were historically distinct. Both are ultimately from Latin.
- One represents the past participle form, casus, of the verb cadere, 'to fall'. This gives rise to the noun casus, in French cas and now in English case. Its primary meaning is "A thing that befalls or happens to any one; an event, occurrence, hap, or chance" (OED). One meaning which developed from this is of great relevance to academic writers: "An instance or example of the occurrence or existence of a thing (fact, circumstance, etc.)." This is the sense which has led to the idea of an ill person being a 'hospital case', of a doctor seeing 50 cases a day, or a lawyer pleading a case, as well as the student's case study.
- The other is derived from the Latin capsa, which means case or receptacle (OED). This is the original which gives rise to all the suitcases, bookcases, spectacle cases and the other forms of 'case', which are all to do with artefacts to put things in. Even a 'staircase', originally the framework into which steps, or stairs, were set, or the 'case', or box, in which the weights and the pendulum of an old long-case, or 'grandfather', clock were hung have the basic menaing of a 'container'. For seeds it should be obvious - many, but not all, plants have their seeds in a seed-case; some fish protect their eggs in egg-cases, commonly called 'mermaid's purses'. :Capsa also gives rise to capsule, which in its original form was simply a smaller container than most cases. (In the seventeenth century, it was userd to label the chambers of the heart.) From the nineteenth century, it has meant the tasteless gelatine which is used to administer doses of nadsty medicine. In the second half of the twentieth, in the form space capsule, it developed the meaning of a container - much smaller than the rocket which carried it - for payloads, like astronauts carried into space.