Onetime source of toothbrush bristles (4)

I believe the answer is:

boar

(Other definitions for boar that I've seen before include "Wild animal, sounds like drill" , "Male swine" , "Resting place for birds or bats" , "The head for drink Falstaff had" , "Sow's mate" .)

I've seen this clue in The New York Times.

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