name of warring state, surname
吴 is primarily a proper noun: the name of an ancient Chinese state and a surname. Its standalone meaning is tied to that historical and family name usage.
吴 is the simplified form of 呉. The older form is thought to depict a person with a tilted head and open mouth, possibly representing a name or a region. The modern simplification replaces the top with 口 and the bottom with 天.
The top 口 (mouth) and bottom 天 (heaven) can be remembered as the name of a state or family: imagine a great mouth speaking from heaven, declaring the name of the Wu state.
For ゴ, think of the English word 'go' — the ancient state of Wu is where history began to go. 'Go' cues ゴ.