What are the two "Black Ones," and why were they named thus?

The two "black ones" are dates and water. This was mentioned in the Hadith of the Two Sahihs on the authority of Aisha, may Allah be pleased with her, who stated that for two months, no fire was lit in the houses of the Prophet, peace and blessings be upon him, and their sustenance was on the two "black ones" (water and and dates). Linguists have explained that Arabs name two things by the more famous of the two. Dates are black, but water is not. However, they were called the "two black ones" by way of predominance, similar to calling the sun and moon "the two moons," or Umar ibn al-Khattab and Amr ibn al-Aas "the two Umars."