Why do we order our adjectives in certain ways: "big, blue house" rather than "blue, big house"?

Melissa Mohr, at C S Monitor, writes:

Explaining the ‘royal order’ of adjective placement

I just finished reading a detective enjoyable little novel. Or was it a little detective enjoyable novel? No, it was an enjoyable little detective novel! The first two sentences are difficult to understand because they violate a rule that native English speakers grasp intuitively: Multiple adjectives must be placed in a particular order.

People learning English must memorize what is sometimes called “the royal order of adjectives” – opinion-size-age-shape-color-origin-material-purpose noun – and then make decisions about which adjectives fit into which categories. Teachers of English as a second language encourage students to remember the acronym OSASCOMP.

[OSASCOMP: (linguistics, mnemonic) Order of adjectives: opinion, size, age, shape, colour, origin, material, purpose [Wikipedia]]

Native speakers are often delighted when they learn about this law and discover how flawlessly they apply it. It even went viral in 2016, when a journalist tweeted about “Things native English speakers know, but don’t know we know.” The tweet attached a paragraph by etymologist Mark Forsyth, explaining the adjective order rule and giving an example that uses all the categories according to the OSASCOMP hierarchy: “a lovely little old rectangular green French silver whittling knife.”

The hierarchy is not absolute, and there is some wiggle room among the “fact” categories – size, age, and so on – in the middle. Contributors to a global grammar discussion board, for example, argued about whether “a new red oval table” sounds better than “a new oval red table,” even though by OSASCOMP the latter would be correct. The order of “fact” versus “opinion” adjectives, however, can’t be altered – opinion comes first.

Surprisingly, this hierarchy seems to be nearly universal among languages that have English-like adjectives. (Not all languages do.) Linguists Richard Sproat and Chilin Shih report that parts of OSASCOMP hold in Mandarin, though only for pairs of adjectives. In Mandarin and English, it’s size-shape, so a “small green vase” is fine but a “green small vase” is not. The Dravidian language Kannada shares size-shape-color.

How did such different, unrelated languages end up with practically the same royal order of adjectives?

Linguists disagree. Benjamin Lee Whorf argued that the order reflects a way of thinking about inherent versus incidental attributes of things. A thing’s purpose and the material from which it’s made are “inherent” and thus placed closer to the noun than its age or size. Drs. Sproat and Shih frame it instead in terms of “absolute” properties, such as color, which are closer to the noun, versus relative properties, like size, which are further away. Whatever the reason, though, it’s a “big black dog” and not a “black big dog” in scattered languages around the world.

Tom Scott did a great video on this a few years ago:

https://www.youtube.com/watch?v=mTm1tJYr5_M

According to the video, there is a "rough guideline" that adjectives should be ordered as follows:

1. General Opinion
2. Specific Opinion
3. Size
4. Shape
5. Age
6. Colo(u)r
7. Origin
8. Construction

He admits there are many exceptions and there is no consensus.

"Why do we ..." questions about language are totally unanswerable based on our current scientific and philosophical knowledge.

The nature and role of what we call 'grammar' in human language is barely understood, and subject to various discussions and theories.

It's inconceivable the even more subtle "why..." question you ask here could be "answered"! One might as well ask: "quickly explain consciousness," say.

I suggest, the reason of order is that we put more important words first. For example "Big grey wolf". We hear first word "Big" - and immidiately we realize that we need pay attention. If we hear first "grey" - we should listen further and don't realize at the moment, how important is the information.

But in accroding with this hypotheis, first word should be the noun? May be. But may be not, and for life of ancient human, size "big" is more important that the noun.