not really a meaning.. kind of like sounds 아이구 is something you can say out of frustration or concern or really anything aish is short for 아씨발 which is kind of like a curse.. nobody has time to say 아씨발 haha.. so they just say aish out of frustration

As a native speaker, I use Aish just exactly the way I would say in English, "Damn"

아이구 has a mild tone of speaking. You can use it when you have something like a backpain so you could say "아이구, 허리야." 아이구 also can be used in a sarcastic way like "아이구, 너 참 잘났다."

These two exclamations can be used similarly or differently depending on the situation. But in general 에이씨 sounds stronger and more harshly than 아이구. They say 에이씨 with foul language in a terrible quarrel. But you can speak 에이씨to yourself to express your frustration. For example, if your laptop doesn't work, you might say "에이씨, 이거 왜 작동안하는거야?"