The word 'yardarm' is a compound formed within the specialized lexicon of English seafaring. Its first element, 'yard', descends from the Old English 'gierd', a general term for a straight rod or stick, which was naturally applied to the wooden spar on a sailing ship. The second element, 'arm', from Old English 'earm', was appended in a figurative sense to denote a lateral projection, much like a branch from a tree or an arm from the body. Thus, the term literally means the "arm of the yard," precisely describing the outer portions of the spar that extend on either side of the mast. This logical compounding created a clear visual metaphor for sailors, distinguishing the ends of the yard from its central section.

Structure: yard + arm - yard: From Old English gierd, meaning a rod, staff, or measure of length. In nautical context, it refers to a spar slung across a mast to support a sail. - arm: From Old English earm, meaning the limb of the body. Here, it functions as a metaphorical extension, meaning a projecting part or branch.