Entries linking to sea-floor
Old English sæ "sheet of water, sea, lake, pool," from Proto-Germanic *saiwa- (source also of Old Saxon seo, Old Frisian se, Middle Dutch see, Swedish sjö), of unknown origin, outside connections "wholly doubtful" [Buck]. Meaning "large quantity" (of anything) is from c. 1200.
Germanic languages also use the general Indo-European word (represented by English mere (n.1)), but have no firm distinction between "sea" and "lake," either by size, by inland or open, 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 in Germanic, and exist in opposite senses (such as Gothic saiws "lake, marshland," marei "sea;" but Dutch zee "sea," meer "lake"). Compare also Old Norse sær "sea," but Danish sø, usually "lake" but "sea" in phrases. German See is "sea" (fem.) or "lake" (masc.).
Boutkan writes that the sea words in Germanic likely were originally "lake," and the older word for "sea" is represented by haff. The single Old English word sæ glosses Latin mare, aequor, pontus, pelagus, and marmor.
Meaning "dark area of the moon's surface" is attested from 1660s (see mare (n.2)). Phrase sea change "transformation," literally "a change wrought by the sea," is attested from 1610, first in Shakespeare ("The Tempest," I.ii). Sea anemone is from 1742; sea legs, humorous colloquial term implying ability to walk on a ship's deck when she is pitching or rolling is from 1712; sea level from 1806; sea urchin from 1590s. At sea in the figurative sense of "perplexed" is attested from 1768, from literal sense of "out of sight of land" (c. 1300).
Old English flor "floor, pavement, ground, bottom (of a lake, etc.)," from Proto-Germanic *floruz "floor" (source also of Middle Dutch and Dutch vloer, Old Norse flor "floor," Middle High German vluor "floor, flooring," German Flur "field, meadow"), from PIE *plaros "flat surface" (source also of Welsh llawr "ground"), enlarged from root *pele- (2) "flat; to spread."
Meaning "level of a house" is from 1580s. The figurative sense in legislative assemblies (1774) is in reference to the "floor" where members sit and from which they speak (as opposed to the platform). Spanish suelo "floor" is from Latin solum "bottom, ground, soil;" German Boden is cognate with English bottom (n.). Floor-plan is attested from 1794; floor-board from 1787, floor-lamp from 1886, floor-length (adj.) of dresses is from 1910. The retail store's floor-walker is attested from 1862.