axillary
/ˈæksəleri/adjective
Relating to the armpit or underarm region
From Latin axilla (Armpit).
Lineage
The story
An armpit once had a surprisingly grand Latin address: axilla could mean not only the human underarm but also the upper arm or the sheltered underside of a bird’s wing. That image explains why botanists use axil for the angle where a leaf meets a stem—the plant’s own little armpit. The adjective reached English in the 1610s as axillary, probably through French axillaire, with the ending reshaped by association with the familiar -ary pattern. The deeper analysis is not completely secure: Wiktionary describes axilla as a diminutive of an assumed *axula, while the supplied evidence does not establish a Proto-Indo-European ancestor. So when a doctor mentions axillary lymph nodes, imagine the body’s hidden wing-fold, not merely a clinical label.
Words from the same roots
axilla · Latin, ‘Armpit; upper arm or underside of an upper wing’
Derivedaxilla, axil, axle, axillary, axillaries