calamus
noun
cal·a·mus ˈka-lə-məs 
plural calami ˈka-lə-ˌmī
-ˌmē
1
a
: sweet flag
b
: the aromatic peeled and dried rhizome of the sweet flag that is the source of a carcinogenic essential oil
2
: the hollow basal portion of a feather below the vane : quill
Example Sentences
Recent Examples on the Web Though the calamus was visible in the 1860s and included in drawings of the fossil at the time, wear on the specimen caused the feature to fade from view. 
Ryan Carney, National Geographic, 30 Sep. 2020
Ryan Carney, National Geographic, 30 Sep. 2020 Word History
Etymology
Latin, reed, reed pen, from Greek kalamos — more at haulm
First Known Use
14th century, in the meaning defined at sense 1a
Medical Definition
calamus
noun
cal·a·mus ˈkal-ə-məs
plural calami -ˌmī, -ˌmē
1
: sweet flag
2
: the aromatic peeled and dried rhizome of the sweet flag that is the source of a carcinogenic essential oil