E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
Trumpet.
To trumpet one’s good deeds. The allusion is to the Pharisaic sect called the Almsgivers, who had a trumpet sounded before them, ostensibly to summon the poor together, but in reality to publish abroad their abnegation and benevolence.
1
You sound your own trumpet. The allusion is to heralds, who used to announce with a flourish of trumpets the knights who entered a list.
