Etymology
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guano (n.)

c. 1600, from Spanish guano "dung, fertilizing excrement," especially of sea-birds on islands off Peru, from Quechua (Inca) huanu "dung."

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guanine (n.)
1846, from guano, from which the chemical first was isolated, + chemical suffix -ine (2).
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batshit 
also bat-shit, by 1967 as a variant of bullshit (n.) in the slang sense; from bat (n.2) + shit (n.). By early 1980s as "crazy," the sense shift is for uncertain reasons; perhaps from the notion of guano as an explosive or health problems caused by inhaling powdered bat feces in caves and mines. Also compare batty "crazy" (early 20c.), from the expression bats in (one's) belfry.
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