Green’s Dictionary of Slang

1. novice.

c.1808		‘A Man of War’ in Holloway & Black II (1979) 168: There’s green-horn fellows, some on board / Before ne’er saw salt water.
1824		Morn. Chron. 17 Aug. 3/5: He derived his support from the rent of his room, and the precarious bounty of ‘green horn’ prisoners.
1901		Sydney Sportsman (Surry Hills, NSW) 20 Feb. 1/4: Back they brings the green horn Johnny, / Always get him, don’t you fret.
1953		T. Runyon In For Life 24: I was collecting what looked to my greenhorn eyes like a million dollars.
1978		(con. 1964) J. Carroll The Basketball Diaries 44: [G]reen horn donkey Irish right off the boat who are nice enough if they ain’t too drunk but who are constantly playing the Clancey [sic] Brothers and shit like that on the box.
1989		(con. 1960s) M. Kingston Tripmaster Monkey 23: Was he hearing English wrong like any greenhorn F.O.B.?
2001		N. Tosches Where Dead Voices Gather (ms.) 269: It was these Sicilian words that were commonly used to describe the work-bosses who lured their greenhorn paesani into servitude in New York City in the early years of the twentieth century.

2. virginal.

1987

R. Campbell Alice in La-La Land (1999) 144: What was she doing with a skinny, greenhorn faggot like that baby-faced schmuck anyhow?