Billingsgate is a proper name: a famous fish market in east London. For hundreds of years it stood by the Thames in the City; the market later moved further east, but the name went with it. English speakers still use Billingsgate to mean that market. For a long time the word also had a second life as ordinary English: Billingsgate meant foul, loud, insulting language, because the people who worked there — an 1811 slang dictionary points especially to the fishwives buying and selling — were famous for shouting and swearing in their deals and disputes, “leaving decency and good manners a little on the left hand.” You will meet that second sense mainly in older books and in set phrases such as “Billingsgate language.” It is not a kind way to talk about working people, and it is not current street English in London now. Though actually, even the insult-sense is a little fossil: a student who says “Don’t use Billingsgate” today will mostly sound as if they have swallowed a history book. Keep the capital B; it began as a place.

比林斯蓋特（倫敦魚市場）；舊亦指魚販式的粗話、髒話