Etymology 1
Attested since the 1840s. Possibly a reference to coffee beans. Attributed to Robert Strang.[1]
Adjective
full of beans (comparative more full of beans, superlative most full of beans)
- (idiomatic) Energetic and enthusiastic.
- Synonyms: feeling one's oats, full of piss and vinegar
1919, P. G. Wodehouse, “The Aunt and the Sluggard”, in My Man Jeeves:"What do you mean by the expression 'Bucks you up'?"
"Well, makes you full of beans, you know. Makes you fizz."
"I don't understand a word you say. You're English, aren't you?"
2006 September 6, Karen Thomas, Lindsey Arkley, “World mourns 'Crocodile Hunter'”, in USA Today, retrieved 6 Nov. 2008:Irwin's friend Chris White reflected on a friendship that began in 1975. . . . "Full of beans, full of life, gung-ho, fearless, tenacious at anything he attempted."
2010, Yvonne Lindsay, For the Sake of the Secret Child, page 68:"The antibiotics are working a treat and he's full of beans. Too many beans, actually. He's asleep now." She gestured to the chaos of the sitting room.
Etymology 2
Attested since the 1930s. A euphemistic form of full of shit.[1]
References
Christine Ammer (2013) “full of beans”, in American Heritage Dictionary of Idioms, second edition, Houghton Mifflin Harcourt, →ISBN, page 160.
- Jonathan Bernstein, Knickers in a Twist: A Dictionary of British Slang (2007): "full of beans — bursting with energy"
- V. S. Matyushenkov, Dictionary of Americanisms, Briticisms, Canadianisms and Australianisms (2010): "full of beans — full of nonsense […] chronically mistaken, wrong"