The Etymology of Bulkhead
Bulkhead is one of those English compounds whose first element has gone obsolete on its own. Modern English has two distinct bulks. The familiar one means mass or volume, descending from Old English bulke. The other, now mostly archaic, meant a partition, framework, or projecting structure such as a market stall — and it descends from Old Norse bálkr (a partition, a balk, a ridge). It is this second bulk that lies behind bulkhead. The compound joined that older bulk to head — meaning upper part or end — to name the upright walls inside a ship that divide its hull into compartments. Recorded from the 15th century in general use and as a fixed maritime term by 1626, bulkhead became indispensable to naval architecture: watertight bulkheads turn a single hull breach into a contained flood and have saved countless ships. The same Norse root bálkr also gives modern English baulk and the related German Balken (beam) and Swedish bjälke.