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".
According to Cobuild (Collins) (Chapter 1:7), the verb + -ing form catenation has three structures (not confusing the non-catenative strings such as Under the trees Bill strolled, looking at the flower beds):
[examples partly adapted]
[1] Verbs in phase (ie a two-verb structure where essentially one two-part concept is expressed):
The sea came rushing in.
He started / kept / stopped crying.
She avoided looking at him.
I won't bother going.
Have you tried asking?
I'm going shopping.
(These mostly invite echo questions such as 'What did he start doing?' 'What won't you bother doing?' With the 'going fishing' type, the echo question would be 'You're going ...?)
[2] Verb with object (ie with what is often termed a gerund)
I like being alone.
Have you considered applying?
She recommended staying.
He didn't remember leaving.
This involves stripping down the engine.
(These mostly invite echo questions such as 'What have you considered?' 'What does this involve?')
[3] Verb with adjunct ( depictive or resultative)
The soldiers died fighting.
Their boat finished up pointing the wrong way.
(These mostly invite echo questions such as 'How did the soldiers die?' (ie What was the manner of their death) 'How did the boat end up?')
I'd argue that these usages are [1] verbal, [2] verbal-nounal, and [3] adverbial or adjectival.
Best Answer
"developing" is not a noun. It's the form of a verb called the gerund, and it has a dual nature, -one of a verb and one of a substantive.
Its verbal nature is shown by a) its ability to take a direct and an indirect object. b) the fact that it can have a subject (I was proud of him being my son) c) is ability to appear in different tenses (he boasted of his having killed her)
Its substantival nature is shown by a) its ability to be the object of a preposition (by doing so)
b) the fact that it can take a plural ending (such going-ons) c) it can take an attributive adjective (his dangerous driving) d) its ability to take a definite or an indefinite article (a hanging was once a public amusement) The active form of a gerund is often used in a passive sense (your hair wants cutting, the garden needs weeding)
In parallel cases a noun ending in e.g. -ment would normally imply the result of an action, the product of an action while the corresponding gerund would refer to the action itself. Take for instance "extension" vs. "extent" or "export" vs. "exportation.
A gerund would normally have in it the verbal nature which the corresponding noun need/does not have. Compare "The king's arrival was met with much enthusiasm" vs. "We are quite tired of his usual arriving very late".
In the case of "developing" one might compare "The development of AIDS in Africa has proved to be one of the biggest tragedies in the Third World" vs "The new president aims at developing the country's poor-relief system".