A lot vs. Alot: 9 Grammatical Pitfalls
past participle adjective from feed (v.). Fed up "surfeited, disgusted, bored," is British slang first recorded 1900, extended to U.S. by World War I; probably from earlier phrases like fed up to the back teeth.
1788, short for Federalist; as colloquial for "official of the federal government," from 1916, especially, after 1930s, of FBI agents.
Any federal government worker or agent, esp in law enforcement or taxation: right up to the day the Feds dragged him into court (1912+)