What did the name “watergate” refer to?

The term "Watergate" referred to the Watergate Scandal the Nixon administration carried out.

Watergate was a major political scandal that occurred in the U.S. in the 1970's following a break-in at the Democratic National Committee headquarters at the Watergate office complex in Washington D.C. in 1972 and president Nixon administration's attempted cover-up of its involvement.

in february 1787, congress decided that a convention should be convened to revise the articles of confederation, the nation’s first constitution. in may, 55 delegates came to philadelphia, and the constitutional convention began. debates erupted over representation in congress, over slavery, and over the new executive branch. the debates continued through four hot and muggy months. but eventually the delegates reached compromises, and on september 17, they produced the u.s. constitution, replacing the articles with the governing document that has functioned effectively for more than 200 years.

i would go with the last one