Q:

[因果]{いん・が}: A bass-ackwards contraction?

In Japanese, we often see where the beginnings of multiple words are taken to make a contraction word.

短大　→　短期大学　→　A juniour college
収支　→　収入と支出　→　income and expenditure; earnings and expenses
国連　→　国際連合　→　The United Nations
リモコン　→　リモートコントロール　→　Remote control(ler)

However, 因果 is an abbreviation for 原因と結果.  I can't say I've seen any other words formed by combining the end pieces.  Why did 因果 come about this way?  Why isn't the abbreviation 原結?
If you have other examples please list them.

Edit:  Oops, yes, of course I meant 結果, not 効果.  I was multitasking and my wires got crossed.

A:

Perhaps the following would reek of Chinese thinking, where 原因 for example is traditionally thought of as two words.
原因 = 因 of the 原, i.e. causing reason
結果 = 果 which has 結, i.e. the produced result
Both words arose in Chinese as a way to eliminate homophones by adding redundant adjectives (obviously all reasons are causing, and all results are produced). The original words are simply 因 and 果; thus they are used in compounds. Put it another way, the compound "因果" probably is older than the words "原因" and "結果", which came after sound changes caused much homophones.
This is similar to how 葉{は} had too many homophones and useless っぱ was added, and 田{た} had too many homophones and んぼ was added; you still use は and た in compounds though.

A:

Do you mean 原因と結果？
因 signifies the cause, as in 原因 or 要因.
果 signifies the result, as in 結果 or 効果.
So when you make the contraction, you are using the kanji that holds those individual meanings. In this case, it wouldn't make sense to not use those kanji. In the example you gave, 原効 doesn't hold the intended meaning.
So in this particular case, it seems the words are derived from Chinese from Sanskrit. See Gogen and Wikipedia JP. I don't know what the technical term is but conceptually, it seem the 原因・結果's relation to 因果 was applied after the fact. I don't think it is like your typical Japanese contraction but it has more to do with the Chinese derivation of the word.

A:

Some may have implied this but let me make it even clearer.
Consider Chinese syntax.
There have been 2-char words in the Chinese languages since long ago. One particular way of coining such words is, to combine two words together with one being the entity and the other being a decorator.
For example:

偏见 ("prejudice", n) is from 偏 ("slanted", adj) and 见 ("view", n).
想象 ("imagine", v) is from 想 ("think", v) and 象 ("image", n).

The basic rule is:

v + n = v
adj + n = n

As we can see:

原因 = 原 ("original", adj) + 因 ("cause", n)
結果 = 結 ("to generate" or "[the] generated"; the implicit subject is the plant, from which the fruit is obtained) + 果 ("fruit", n)

Although 結果 is v+n, it is not used as a verb in real use. Instead, it is used as a noun or a conjunction. So when 結果 is used as a noun, it inherits the part of speech of 果.
In result, if you would like to coin a new contradiction-style 2-char noun based on two 2-char nouns, the best way should be to pick up their noun parts, respectively.

Further readings:
The Chinese languages don't necessarily distinguish parts of speech in writing. 想象 ("imagine", v, "imagined", past, "imagined", past participle), 想象 ("imagining", present participle), 想象 ("imagination", n), 想象 ("to imagine", infinitive), 想象的 ("imaginative", adj), and 想象力 ("imaginative force", n) all use the same substring "想象".

