noun
also nicker or nicker-seed or nick·ar nut ˈnikə(r)(-)
( -s )
Etymology: nicker, probably from obsolete nicker marble, modification of Dutch knikker, from knikken to crack, snap, from Middle Dutch cnicken, probably of imitative origin like Middle Low German knicken to crack, snap, Middle High German knacken to make a cracking noise — more at knack
: the very hard shiny gray seed of bonduc (sense 2)