On the poetic front, "ai-ki-do" 合 氣 道 is onyomi, meaning it is pronounced (more or less) as a Japanese pidgin of Classical Chinese. The connotations appropriate to onyomi in poetry are Chinese in origin, with whatever other gloss the Japanese have given it, not unlike Latinate words in English.
Actually, "ai" is kunyomi. The onyomi of that character is "go". The compound "aiki" is a mixture of onyomi and kunyomi - if it was read entirely as onyomi it would be "goki". It's rare to have a word mix the two, but it does happen.
My guess is that whoever coined the term "aiki" was actually trying to distance themselves from the classical Chinese meaning of the compound "he qi", which originally referred to a Tianshi Daoist sexual rite from probably the 2nd or 3rd century AD. The term originally meant "the uniting of the qi". The qi involved being that of the two people, and knowing the Daoists, probably the qi of various constellations, stars and other things.