There is a clue in lexicography from an ancient dictionary written around 1st century BC, where it is the oldest text we know started to use the word 圍棋 (but written as 圍棊) to refer to Go. And it seems to be a new word or regional word since the description of the word is only one line - 圍棊謂之弈。自關而東齊魯之間皆謂之弈, translated as Go is also called yi(弈), in the eastern part of China, they all call it yi 奕 in two of the ancient powerful states Qi 齊 and Lu 魯. These states existed since the very early day of the Zhou dynasty before the 1st millennia BC and were high nobles. Confucius himself came from one of them, and Confucius was also one of the earlier scholars to mention yi 奕 in his work. So we are fairly certain at the 1st millennia BC, Go or the precursor that continued to use the same word for nearly a thousand years is some kind of game that high nobles were playing (but perhaps only popular in this part of China). And in old Chinese literature, if something only uses one character with a simple form, it usually means it has a very ancient origin rooted in old Chinese language, where double characters word like 圍棋 are used when people found something similar and added an additional word to distinguish them (like chess, and Chinese chess).
So, we know there was some kind of games called qi 棊, that existed at the time, which is slightly different than yi 弈. And people added the word “encirclement” 圍, to emphasize the difference. Hence in 1st century BC, it was at least a game about who gets a larger part of the board. And it begs a question, is it possible qi 棊 in itself actually wasn’t a game about encirclement?
There is a second clue right before the yi 奕 entry - "簙謂之蔽，或謂之箘，秦晉之間謂之簙，吳楚之間或謂之蔽，或謂之箭裏，或謂之簙毒，或謂之夗專，或謂之𠥙璇，或謂之棊。所以投簙謂之枰，或謂之廣平。所以行棊謂之局，或謂之曲道。 "
I won’t be translating them all, but the long descriptions basically boiled down to a list of words that all refer to the game 簙 in different regional dialects (蔽,箘,箭裏,簙毒,夗專,𠥙璇), and the most interestingly - qi 棊 as well. This means some people (probably not many since it is listed in last) also used the word 棊 for a different type of game 簙. It gets more interesting that we know the Imperial families of the Han dynasty (the time period where this dictionary is composed) came from a place called Song 宋, where it used to be a minor state. But Song got conquered around the 3rd century BC by no other than its powerful neighbor - the state Qi 齊 (one of the two powerful states I mentioned above where people call the game of Go - yi 奕).
So the most likely scenario is that Go in its precursor form (no matter what it was) was popular in the eastern part of China in these two powerful states for ages. At the same time, a family of games (possibly way older) was also popular throughout China but already split into various forms in different local states and take roots in regional dialects. Where one of the state Song 宋 has a variation called qi 棊. When the Song state was incorporated into the neighboring Qi state, people started to borrow words and adapted Qi culture, and start to play the imported yi 奕 game. But in oder to distinguish them, they used an additional word to describe yi 奕 as 圍棊. Luckily, the people from this region gave rise to the family later forming the powerful Han dynasty who speak the local dialect, and brought the game to their new center of power in the western part of China, and spread it across Han territory.
However, we are leaving with one question - what exactly was this widespread family of games (簙,蔽,箘,箭裏,簙毒,夗專,𠥙璇,棊) about, and makes the people from Song 宋 used it as an analog for yi 奕? We have some clue about what it is - It was some kind of bo 博, later a variation called Liubo 六博 became very popular throughout the Han dynasty as well. But we are not sure the reconstruction of its rules is complete, and how much was it differed from the older bo 博, and how much regional difference between each variation. Although, they are definitely popular enough to be used together as 博奕, representing boardgames in general.
The strange thing is that we have archeological artifacts for Liubo 六博, which have gameboards (it has two boards, one for moving the pieces, one for the rods related to keeping scores and using several types of dices/rods) that is very different from Go, and it is a game involving chances, and generally considered as a type of mixed racing and capturing game. Although its gameboard will immediately remind people of the board used in Nine men's morris - Wikipedia, and also astrology maps (I think this is the reason why Go seems to be associated with astrology often and it might still be true). It is possible that the precursor developed in Qi and Lu states were modified from a common ancestor game that diverged into various kinds, and kept as peasants game in the form of bo 博 due to its gambling component, while yi 奕, popular for the upper-class evolved in a very different direction, and became more sophisticated.
One final thing very interesting and worth noting is that there was a third type of game called Sai (賽 I swear it’s just coincident), that was often associated with bo 博, and the difference seems to be that Sai 賽 doesn’t involve the gambling/chance component, but was purely a game of skill. There are some debates as to what it was, and there is just too little evidence to know for sure. I suspect that it was probably a kind of shaped rearranging game similar to Fangqi which has some common roots with bo 博, and split off earlier from some primitive games (maybe a type of merels/morris) where their gameboards can be all kinds of sizes and designs (astrology cultures could be mixed in before this early stage or even possibly be the inspiration of it). The variations involved more with moving and capturing became the skill part of bo 博, while the capturing and shaped rearranging components were focused in Sai 賽 (probably with different types of boards, and some used grid boards evolved into Fangqi today).
Hence if we trace back the origin of Go, one likely path might be this.
-
Thousands of years ago beyond recorded history, some astrology concepts inspired or got mixed in with a primitive type of merels/morris games.
-
It split off into the precursor of Bo 博 with components of gambling, moving and capaturing, where the precursor of both Sai賽 and proto Go focused more on shape arranging, strategy placements, moving and capturing.
-
The precursor split into Sai 賽 which focused more on shape arranging, moving and capturing (and later on continue to evolve into Fangqi), where the precursor of Go - yi 奕 focuses more on strategic placement due to being introduced to wealthy upper class, but still maintain the capturing and possibly some moving components, where people hundreds of years later, still were able to recognize its similarity to a variation of 博 - qi 棊.
-
During the Han Dynasty, the alternative name of yi 奕 - 圍棊, maybe a variation of yi 奕, were popularised by the imperial families and maybe kept refined its rule to be more generalized, and possibly focused more on encirclement, and loses the component of moving, and has some kind of ko rules that were still incomplete.
-
During the first half of the 1st millennia AD, 圍棊 started to become 圍碁 Weiqi, where the stones no longer used wood as common materials, and as it spread to different regions, different ko rules, scoring rules, even suicide, forbidden spots, atari sequences were evolved, and due to China split several times into several regional powers, and re-integration was short-lived, these differences were kept. Some variations spread to neighboring regions like Tibet, Korea, central Asia, until the next reunification in the Tang Dynasty in the 7th century AD, where the mainstream scoring rule - counting road method replaced others (like the primitive 溢 scoring requiring whole board filling), and ko rules started to mature and simplified to the form we can recognize today.