high-seas

The term "high-seas" is a compound formed from two native English words. "High" in this context does not refer to physical elevation but carries an older, figurative sense of "chief" or "main," as seen in terms like "highway" or "high altar." "Seas" is the straightforward plural of "sea." The compound emerged in Middle English to specifically denote the open, unenclosed ocean, the "main sea" far from any coast. This concept evolved legally to refer to international waters, the vast maritime areas beyond the territorial claims of any nation, governed by the principle of freedom of the seas.

Structure: high (elevated) + seas (bodies of salt water) - high: From Old English hēah, of Germanic origin; related to Dutch hoog and German hoch. In this compound, it functions as an adjective implying "chief, principal, or remote from shore." - seas: From Old English sǣ, of Germanic origin; related to Dutch zee and German See. It functions as the plural noun denoting the large expanses of salt water.