Beware of after-claps
An after-clap is a catastrophe or threat after an affair is supposed to be over. It is very common in thunderstorms to hear a “clap” after the rain subsides, and the clouds break.
What plaguy mischief and mishaps Do dog him still with after-claps.
—Butler: Hudibras, Pt. i. 3.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894