Learn English – How did the word “beaver” come to be associated with vagina

When you flog a horse you make it go faster. So to flog goods is to make them move faster.

It's associated with the Holocaust for this reason:

While the phrase “Never Again” was in use before World War II — it was the title of several early American films — it has, for Jews, become shorthand for an ongoing commitment to remembering the Holocaust. The phrase was first popularized as a Jewish rallying cry by militant Zionist leader Meir Kahane in his 1972 book “Never Again!: A Program for Survival.”

The book of a Zionist leader has made this phrase of special meaning to the Jews. The book was about the survival of the Holocaust attempt of the Jews.

The usage of "Never Again" might have first appeared on handmade signs put up by the inmates, but it didn't gain special meaning until Meir Kahane wrote his book.