cuttlebone
noun
cut·tle·bone ˈkə-tᵊl-ˌbōn 
: the shell of a cuttlefish that is sometimes used for polishing powder or for supplying cage birds with lime and salts
Example Sentences
Recent Examples on the Web The soft-bodied creatures, which rely on an internal bone called a cuttlebone to control their buoyancy, include more than 100 different species. 
Corryn Wetzel, Smithsonian Magazine, 21 Aug. 2021 Some sources say squirrels also appreciate and will use a cuttlebone (usually sold for pet birds and gnawing rodent pets) secured to a tree or a stake. oregonlive, 17 Oct. 2020
Corryn Wetzel, Smithsonian Magazine, 21 Aug. 2021 Some sources say squirrels also appreciate and will use a cuttlebone (usually sold for pet birds and gnawing rodent pets) secured to a tree or a stake. oregonlive, 17 Oct. 2020 Word History
Etymology
Middle English cotul cuttlefish (from Old English cudele) + English bone
First Known Use
1547, in the meaning defined above