Plural of guano; seabird or bat droppings, especially those accumulated in large deposits and valued as a rich nitrogen fertilizer.
From Spanish guano, from Quechua wanu (Peruvian/Andean language), meaning 'dung'; the Spanish colonizers encountered massive deposits on Peruvian islands and exported the term globally.
Guano was so valuable in the 1800s that entire wars were fought over guano islands, making bird poop one of history's most contested natural resources!
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