(Aun no kokyuu; “Breathing Ah–Un.”)
Two parties, in a mutual activity, achieving a state of perfect mental, physical, and spiritual harmony. It’s common knowledge that there is a state one can enter when wholly concentrating on some activity, known colloquially as “the zone” or “the groove.” It’s a very Zen state where all distractions vanish and perfect focus is achieved. Now imagine that happening in a partnered activity – figure-skating or music-making, of course, but also handiwork, if there are any professions left that call for pairs.
阿吽 (aun) is supposedly the Japanese rendition of the syllable “Om.” Coincidentally, it also represents the first and final sounds of the modern Japanese syllabary, which begins with あ (“ah”) and ends with ん (“n,” also pronounceable as “un”). の (no) is commonly explained in English as a possessive particle, although in this case the use is more associative – that is, showing a relationship. 呼吸 (kokyuu), a compound literally comprising the characters for “breathe out” (or “call”) and “breathe in” (or “suck”) and therefore indicating respiration in a general sense.
Translated literally, the phrase becomes “Breath of Om” or “Breath of Ah-Un.”
吽 can also be written 呍 – although the latter character is sufficiently archaic and rare that I’m not sure it will even display for you properly. (Just in case: it looks like 伝 with a “mouth” radical on the left instead of a “person.”)
Meanwhile, there’s a lot going on here! Among other things, this saying is associated with the 狛犬 (koma-inu) that guard many Japanese shrines. These statues (generally thought to represent lions or dogs) almost always come in pairs; one with its mouth open as if saying “Ah”; the other with its mouth closed as if saying “mm” (which in Japanese orthography is still ん, and equivalent to “un”). The harmony indicated by the saying can therefore be thought of as referring to the concord of the stone guardians.
Beyond that, there’s a huge amount of mystical association being made. “Om” itself ties back to Hindu and Buddhist practices, while “respiration” invokes meditative practices. (The Zen reference above was no accident.) A full exploration of the topic would doubtless fill a book.
The interesting thing to me is that a phrase so deeply tied to the inward practices of breathing and meditating on the syllable “Om” has come to refer to an external connection with another human being. I have no doubt that work-partners can and do attain a state where they act together with intuitive understanding and no need to actually speak. And I have no doubt that people who have experienced both the lone and partnered versions can attest to their similarity. Why this saying only refers to the latter, though, is a mystery – perhaps from the need to write the syllable with two characters in Japanese? The association with guardian statues that are paired for an unrelated reason?
Final note: One of the definitions I read said that more than two people can be involved, but this seems not to be common usage.
(“Shishou to deshi wa tsune ni aun no kokyuu de hitokoto mo iwazu ni hataraiteiru.”)
[“The master and apprentice are always working in a state of Zen harmony without a single word between them.”]