brake (n.2) Look up brake at Dictionary.com
kind of fern, early 14c.; see bracken.
brake (v.) Look up brake at Dictionary.com
"to apply a brake to a wheel," 1868, from brake (n.1). Earlier, "to beat flax" (late 14c.). Related: Braked; braking.
brake (n.1) Look up brake at Dictionary.com
mid-15c., "instrument for crushing or pounding," from Middle Dutch braeke "flax brake," from breken "to break" (see break (v.)). The word was applied to many crushing implements, especially the tool for breaking up the woody part of flax to loosen the fibers. It also was applied to the ring through the nose of a draught ox. It was influenced in sense by Old French brac, a form of bras "an arm," thus the sense "a lever or handle," which was being used in English from late 14c., and "a bridle or curb" (early 15c.).

One or the other sense or a convergence of all of them yielded the main modern meaning "mechanical device for arresting the motion of a wheel," which is attested by 1772.
brake (n.3) Look up brake at Dictionary.com
"thicket; place overgrown with bushes, brambles, or brushwood," mid-15c., originally "fern-brake, thicket of fern," perhaps from or related to Middle Low German brake "rough or broken ground," from the root of break (v.). Or, more likely, from Middle English brake "fern" (c. 1300), from Old Norse (compare Swedish bräken, Danish bregne), and related to bracken. In the U.S., applied to cane thickets.