“Good to go” is an English idiomatic expression that means someone or something is ready for action, and no further delay is necessary. It has often been used informally in group activities where teamwork is vital to success, such as in business sales, sports, or military actions. When someone says that he or she is “good to go,” it means that he or she is eager to get started on an activity and wants to set aside all peripheral matters and cause for delay.
While tracing the meaning of idioms and their origins can almost always prove problematic, they usually retain some intent or connotation that points to a specific direction for their most frequent use. Some sources attribute this particular phrase to such unique origins as the marketing of a popular brand of baked goods in the US in the 1960s and 1970s, which were advertised as “...snacks and cakes, they're good to go!” In popular slang, the phrase is also said to represent when a man thinks a woman is interested in sexual activity.
The basic intent is to convey a sense of readiness and, in that respect, the expression most likely originated in US military terminology, possibly from the US Marine Corps, who are almost always the first troops sent into a conflict, or aviation sectors. It has been said that Marine units would often communicate with each other remotely by radio and confirm that each squad was ready to go before launching an attack. There is also speculation that the phrase is related to the process of an aircraft pilot going over a pre-flight checklist. Once completed and before taking off, the officer would signal to a copilot or other airmen that he or she was “good to go” when ready to start the takeoff procedure. The early days of the space program may also have served as an origin for the phrase, when astronauts confirmed their status before a final launch procedure was initiated.
While its origins are obscure, the phrase is commonly used in the US. Like many idioms, it has an alliterative ring to it that lends itself easily to memory and conversation. It is also a concise and friendly way for someone to express that he or she is tired of waiting around for something to happen, without being openly offensive by saying so.