Aisho was originally derived from the part of the philosophy of Onmyo gogyo (Yin-Yang Wu-Xin), which explained that when the attributes of all things influence each other in a good way, they become stronger; when they balance out the good qualities in each other, on the other hand, this invites bad situations.
相性の、元々の意味は陰陽五行思想の一端で、全ての事物が持つ属性が、相互に良い意味で影響しあってより強まるか、逆に相互の良い部分を相殺しあって悪い状態を招くかといったものである。