Merlon

A merlon, in architecture, forms the solid part of an embattled parapet between the embrasures, sometimes pierced by loopholes.

The word comes from the French language, adapted from Italian merlone, possibly a shortened form of mergola, connected with Latin mergae (pitchfork), or from a diminutive moerulus, from murus or moerus (a wall). An alternative etymology suggests that the mediaeval Latin merulus functioned as a diminutive of Latin merle, expressing an image of blackbirds sitting on a wall.

Original text from 1911 Encyclopaedia Britannica