Green’s Dictionary of Slang

1. (US) Chinese.

1903

Ade ‘Hickey Boy and the Grip’ in In Babel 110: Me settin around on my shoulder-blades lookin like one o’ these bamboo boys full o’ hop.

2. used of a Westerner who has ‘gone native’ while stationed in the Far East; thus of the accented Eng. some use (see cite 1934).

1922		Hospital Corps Qly 20-23 31: [...] eventually earning for themselves the contempt of their more self-respecting shipmates and being rewarded with that most degrading of all titles known in the islands as ‘Bamboo American’.
1934		E. Hahn China to Me 117: [His accent has] a little bit something else hard to describe, although a lot of people out East get it. We call it ‘bamboo American.’ I am tainted with it myself, I suppose.
1940		Life 28 Oct. 99: Squacks are the native girls of the Pacific sometimes taken to mistress by sailors who assume the title of Shackmaster, and become Bamboo Americans.
1942		W.L. White They Were Expendable 97: There was, for instance, a bamboo American— some man who’d married a Filipino wife and gone native— who managed a big pineapple plantation.
1971		Fraud & Corruption in Management of Milit. Clubs 877: An inquiry into Crum's background showed that he was a so-called ‘bamboo American,’ having been born in Shanghai, China, in 1918, and having lived most of his life in the Far East.
2004		J.H. Bishop Coll. of Stories 77: Bamboo Americans are former American soldiers and businessmen, usually married to Asians, who after World War II or Vietnam loved the oriental lifestyle [...] and never went home.
2009		(con. WW2) P. French Through the Looking Glass 213: Durdin was still working for the New York Times and was by now firmly a bamboo American but he never became overly pro-communist.

3. eccentric, mad [f. sense 2].

1961

(con. early 1950s) J. Peacock Valhalla 322: Was he going bamboo? No, he wasn‘t going bamboo. He knew what he had to do.