Curtain lectures

Curtain lectures
private admonitions given by a wife to her husband

The phrase, though of earlier origin, is immortalized in the celebrated 'Mrs Candle's Curtain Lectures' by Douglas Jerrold, published in the columns of Punch, 1845

Curtains = bed curtains, the lectures being delivered at night.

'Beside what endless brawls by wives are bred,
The curtain lecture makes a mournful bed.'
Dryden


Source: James Main Dixon, English Idioms, Thomas Nelson & Sons Ltd, London & Edinburgh 1944, p.62