E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Diplomatic Cold (A).
An excuse to get over a disagreeable engagement. Mr. Healy, M.P. (1885), said that Lord Hartington and Mr. Gladstone had diplomatic colds, when they pleaded indisposition as an excuse for not giving addresses at public meetings in which they were advertised to speak. The day after the meetings both gentlemen were much better.