I. -ˌdau̇n adjective
Date: 1934
1.
a. of a collar : having the ends fastened to the garment with buttons
b. of a garment : having a button-down collar
2. or but·toned-down -t ə n-ˌdau̇n : conservatively traditional or conventional ; especially : adhering to conventional norms in dress and behavior
button-down businessmen
II. noun
Date: 1952
: a shirt with a button-down collar