mer·lon (mûr'lən) n. A solid portion between two crenels in a battlement or crenelated wall.
[French, from Italian merlone, augmentative of merlo, battlement, perhaps from Medieval Latin merulus, from Latin, merle (from their imagined similarity to blackbirds sitting on a wall).]
"solid part of a battlement," 1704, from Fr. merlon, from It. merlone, aug. of merlo "battlement," perhaps a contraction of mergola, dim. of L. mergae "two-pronged pitchfork."