Trending: ‘what's sauce for the goose is sauce for the gander’

Searches for a certain chiefly British phrase spiked on September 3, 2019, after British Prime Minister Boris Johnson responded to a question about whether members of his own Conservative (or Tory) party who vote against his proposed deal with the European Union would be effectively kicked out of the party (just like those who have announced that they would vote against a "no deal" Brexit). He answered yes, saying:

"What's sauce for the goose is sauce for the gander"

What's sauce for the goose is sauce for the gander is used to say that one person or situation should be treated the same way that another person or situation is treated.

It's the British version of the idiom more commonly known in American English as what's good for the goose is good for the gander.

There are many English idioms that are very slightly different in British and American English, for example put out to pasture becomes put out to grass in British English.

Both expressions seem to date from the 17th century, and evidence for the good version is slightly earlier than the sauce version:

We'l flatter as well as they,

For they that can break a vow,

Teach women what they shall be

If to play fast and loose

Be good for the Goose,

Tis good for the Gander too.
— Anonymous, The forsaken maids frollick or, A farewell to fond love, 1666

Trade will evidently be augmented by the instance of most flourishing Commonwealths, which have ever begun with it, and the proverb tells us, what is sawce for a Goose, is sawce for a Gander.
— Thomas Culpeper, The necessity of abating usury re-asserted in a reply to the discourse of Mr. Thomas Manly entituled, Usury at six per cent. examined, &c., 1670

Using sauce rather than good for this idiom can put a different light on its meaning: when we say something is "good for you," we think of something that conveys benefits. But when sauce is used, we understand that the condiment is likely chosen by someone else, and conforms to the taste and will of others who control the situation.