Why the perfect language has to be both orderly and random- Article from www.io9.com

Why the perfect language has to be both orderly and random 

If you try to figure out the connection between how words sound and what they mean, you'll be working for a long, long time. While patterns do exist, most language sounds are random...and there's a very good reason for that.
Languages don't really make much sense, at least not from a strictly logical sense. Let's say you were designing a language from scratch. Wouldn't it make sense to associate very big things with correspondingly long words, and to make small words only refer to tiny things? That obviously isn't how it works in English, at least not with any regularity - look at "star" and "microorganism", for instance.
Sounds are similarly chaotic. There are a few areas where it's possible to find so-called "pockets of systematicity", in which certain language sounds tend to cluster around the same basic concept. As Sara Reardon explains in ScienceNOW:

Many English words beginning with "sn," for instance, tend to have something to do with the nose: sneeze, snort, snot. In many languages, vowels made with the back of the tongue, such as "o" and "ah," tend to appear in words that describe something big (boulder), whereas vowels made at the front of the mouth, such as "ee," often denote something smaller (flea). It's unclear why these "pockets" exist: whether they're accidents or are somehow tied to language learning.

And yet these pockets are, at best, vague correlations. They're not strong relationships, and it's easy to find tons of counterexamples for all of this. To test why this is, Lancaster University researcher Padraic Monaghan used a computer to create a series of alien languages, which he then attempted to teach to test subjects. Some of these languages were completely orderly, in which sounds, word structures, and meanings were closely intertwined. The other group of languages were completely arbitrary.
As it turns out, the test subjects had tremendous difficulty learning either type of language. He then started mixing up the sounds within the words, so that the orderly language was no longer truly systematic - a big thing might be described by a long word, but its vowel would now be an "ee" sound. The test subjects had a much easier time learning this language.
The trick, Monaghan believes, is that no language can be truly orderly. If it was, words with similar meanings would sound too similar for people to easily tell them apart. This would make it prohibitively difficult to build up a vocabulary, and so the apparent randomness builds in enough variety for words to be manageable. Of course, if languages were completely chaotic, they'd be just as impossible to learn. The key here is balance.