"ornamental clasp consisting of a pin and a covering shield," early 13c., from Old French broche "long needle" (see broach (n.)). Specialized meaning led 14c. to distinct spelling.
Entries linking to brooch
broach n.
"pointed instrument," c. 1300, from Old French broche (12c.) "spit for roasting, awl, point end, top," from Vulgar Latin *brocca "pointed tool" (source also of Spanish broca, Italian brocca), noun use of fem. of Latin adjective broccus "projecting, pointed" (used especially of teeth), perhaps of Gaulish origin (compare Gaelic brog "awl").