This article first appeared as the second part of the taichido.com newsletter issue 65 as draft preview of a book that remains a work in progress.

The most obvious assumption is that the "do" in "taichido" refers to the "do" - as in Judo, Aikido and Budo. Obvious because these are all, like Tai Chi, martial arts. But then again, those with even the least amount of knowledge would know that Tai Chi is of Chinese origin whereas all of those others mentioned are Japanese things. Therefore - it may refer to the "tao" or dao as in Taoism. In taichiDO it is, I think, meant to mean a little of each! It might also mean/suggest ... in English ... just ... DO taichi!

Whatever, in both cultures, the word and incumbent concepts and connotations of "DO" is derived from the Sanskrit MARGA - meaning the 'path' or 'way' ... 'to enlightenment'.

I have here separated the words 'path or way' from 'enlightenment' to highlight a fundamental difference in the Chinese and Japanese concepts of this word. For the Japanese it is 'the way towards enlightenment', but for the Chinese it is more just 'a way'; like the way of the gardener or the way of the poet, or the brick layer, and so on. Just a way [in Chinese terms] that corresponds roughly to the order expressed in the totality of natural (physical) laws.

For some further clarification of the Japanese way of looking at this word DO we could look at the word BUDO.
Budo is a compound of the word bu, meaning war or martial; and do, meaning path or way. Bu may also be interpreted as meaning "courage".

Do as in Budo
In Japanese it is an experiential term, experiential in the sense that practice (the way of life) is the norm to verify the validity of the discipline cultivated through a given art form. The modern budo has no external enemy, only the internal enemy, one's ego that must be fought.

From Budo @Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Budo: "The term refers to the idea of formulating propositions, subjecting them to philosophical critique and then following a 'path' to realize them."

Budo arts are derived from the combat arts - they did not develop independently of them. Contemporary budo forms can be traced back to the Japanese hereditary warrior class, the Samurai (bushi).

Bujutsu
Similarly to budo, bujutsu is a compound of the words bu, and jutsu, meaning science, craft, or art. Thus, budo is most often translated as "the way of war", or "martial way", while bujutsu is translated as "science of war" or "martial craft." However, both budo and bujutsu are used interchangeably in English with the term "martial arts".

Budo is ultimately a commitment to a way of life dictated to enhancing the most creative and altruistic qualities of human character and the simple and practical virtue of budo martial discipline is that it is an excellent means of awakening courage by means of some attendant philosophy and correct moral doctrine.

"Tao" @Wikipedia [http://en.wikipedia.org/wiki/Tao] it says:
In Classical Chinese philosophy there is Tian dao (sky or natural dao, usually translated religiously as "heaven's Tao") Da Dao (Great dao, the actual course of all history, everything that has happened or will happen) and Ren dao (human dao, the normative orders constructed by human (social) practices). The natural dao corresponds roughly to the order expressed in the totality of natural (physical) laws. The relations of these three were the subject of the discourses of Lao Tsu and Confucius.

Thus, in Chinese terms tao or dao (or do?) is an experiential term (a thing ones 'does') and in Japanese terms a way of attaining courage through the practice of correct moral doctrine.