President Martin Van Buren was called "Van Ruin" because?

Martin Van Buren said that the two happiest days of his life were his entrance into the office of President and his surrender of the office. While his political opponents were glad to see him go—they nicknamed him “Martin Van Ruin”—many Americans were not. ... This environment gave young Martin a taste for politics.

Explanation:

In 1840, Martin Van Buren was unanimously nominated as the Democratic candidate, but the challenges and controversies of his first term proved too great to overcome (they had also earned him the nickname “Martin Van Ruin”). ... Van Buren finished out his term, and in 1841 returned to his “Lindenwald” estate in Kinderhook.

It was because his first term was so great

Explanation:

a phrase from a poem by ralph waldo emerson about the battle of lexington and concord. emerson's words read, “here once the embattled farmers stood / and fired the shot heard round the world.”