Firstly, there’s a number of ways in classical Japanese to describe the act of striking, hitting, smashing, thrusting, and pushing in regards to jujutsu. One common term to describe punching, for example, is ‘tsuki’ (突), which emphasizes a thrusting, or stabbing through. While a term for hitting, in the sense of striking with a stick or hammer, is ‘uchi’ (打). For some reason during my various translation projects, I have come to have an appreciation for ‘ate’ (当). This character gives an impression of striking sharply, such as with a specific knuckle, finger, or toe. a sort of “stabbing into” rather than “stabbing through” as with tsuki.
And the ‘mi’ (身) of ‘atemi’, is commonly translated as ‘body’, or sometimes “self” as in the term ‘sutemi’ (self-sacrifice; 捨身). So together ‘atemi’ (当身) can come to mean “striking the body”. However I wouldn’t be much of a researcher were I to settle on simple modern translations when referencing classical texts on jujutsu…
The character ‘ate’ (當) is derived from a combining of ‘kuwaeru’ (尚), meaning “to add to”, “further”, or “increase”; and ‘den’ (田) which means a field or farm. It can be a little difficult to see first how 尚 and 田 come together to make 當, only when you overlap, and also recognize the context in which the two characters were used together in classical literature, then you can see the merge to what transforms into 當 “to hit”, “aim”, “put or place against”, and even “to expect”. The form of 當 had been simplified in the early Edo period (1603-1868) to become 当, which is the writing that I prefer for aesthetic reasons.
身 on the other hand, is kind of interesting because it is the pictograph of a pregnant woman, with the fetus adhering inside. However, it’s been over a thousand years since it referred in any way to a woman or pregnancy. Nowadays, it refers to the “self”, but not simply of the physical body, but the entire self. Everything that makes up the person, the self, the being. Including the psychology, anthropology, sociology, the psycho-physical relationship, the ego, the id, the super ego, even the extended being (the influence that the being imposes on it’s environment. 身 is the consistent part of the human being.
Therefore, we can interpret ‘atemi’ (当身) as “the action of striking the deepest part of the being in front of you”.
In it’s context, the classical jujutsu method of atemi is to strike in a very exact way that not only inflicts physical percussive harm, but also allows for one to attack the psyche, the balance, the energy (meridians), or even to strike in a subtle way that inflicts no pain or injury at all, but with the same end result of unbalancing, breaking the posture, shifting the position, harming or even killing.