by size or by salt vs. fresh. This may reflect the Baltic geography where the languages are thought to have originated. The two words are used more or less interchangeably, and exist in opposite senses (e.g. Goth. saiws "lake," marei "sea;" but Du. zee "sea," meer "lake"). Cf. also O.N. sær "sea," but Dan. sø, usually "lake" but "sea" in phrases. Ger. See is "sea" (fem.) or "lake" (masc.). Meaning "dark area of the moon's surface" is attested from 1667 (see
mare (2)). Phrase sea change "transformation" is attested from 1610, first in Shakespeare ("The Tempest," I.ii). Sea legs is from 1712; sea serpent attested from 1646; sea level first recorded 1806. At sea in the fig. sense of "perplexed" is attested from 1768, from lit. sense of "out of sight of land."