Etymonline has this to say:
-ics
in the names of sciences or disciplines (acoustics, aerobics, economics, etc.) it represents a 16c. revival of the classical custom of using the neuter plural of adjectives with -ikos (see -ic) to mean "matters relevant to" and also as the titles of treatises about them. Subject matters that acquired their names in English before c.1500, however, tend to remain in singular (e.g. arithmetic, logic).
So yes, at some point in history, there were such things as physic (meaning "natural science"), mathematic (meaning "mathematical science"), etc. that were later turned into plural forms but kept being treated as singular.
Edit: having looked in a few more places, it appears that in contemporary English, it still makes some sense to have both the suffix -ic and its plural form -ics. According to the Collins English Dictionary, the former has kind of specialized in forming adjectives, while the latter is happily forming nouns:
-ic
suffix forming adjectives
- of, relating to, or resembling: allergic, Germanic, periodic. See also -ical.
[...]
[from Latin -icus or Greek -ikos; -ic also occurs in nouns that represent a substantive use of adjectives (magic) and in nouns borrowed directly from Latin or Greek (critic, music)]
[...]
-ics
suffix forming nouns (functioning as singular)
- indicating a science, art, or matters relating to a particular subject: aeronautics, politics
- indicating certain activities or practices: acrobatics
[plural of -ic, representing Latin -ica, from Greek -ika, as in mathēmatika mathematics]
The key here is that they are not just two unrelated suffixes. Much rather, one is etymologically a plural form of the other. As the American Heritage Dictionary succinctly puts it, -ics is "-ic + -s".
North as an adjective (and other cardinal points) is never capitalized, except when part of a construct that is capitalized in itself, such as a country name (North Korea, South Africa).
As a noun, it is capitalized when used in the game of bridge (North and South play together) and, more commonly, when designating a known part of a country (Virginia joined the North) or of the world (the mysterious East, the history of music in the West).
Best Answer
The words orient and occident are two of the set of six French words
which form the set you were looking for. The word septentrion (north) is obsolete in English, and I can find no evidence that midi (formerly spelled midy) was ever an English word at all.
In Old French, the word méridien was used instead of midi (see wikipedia), so another possible sixth term is meridian, which is indeed an English word which has occasionally been used to mean the opposite of septentrion; see for example this reference from Google books. So maybe the best answer is:
You shouldn't expect anybody to understand the meaning of the last two terms without explanation, though.