More on John Chinaman from Infoplease:

• John Chinaman - John Chinaman Either a Chinese or the Chinese as a people. Source: Dictionary of Phrase and Fable, ...
• Biddy - Biddy (i.e. Bridget). A generic name for an Irish servant-maid, as Mike is for an Irish labourer. ...
• Dictionary of Phrase and Fable: J - Definitions, origins, and illustrative excerpts for words, phases, and literary allusions starting with "J"