Green’s Dictionary of Slang

underdone adj.

[cooking imagery]

said of one who has a pale complexion.

1900
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1909
[UK]Sporting Times 10 Feb. 2/5: The underdone son of a gun, conceited ignorant prig! / Passing his tin-pot judgements on the generals of the day.
[UK]J. Ware Passing Eng. of the Victorian Era.