sea-power n.

Middle English se, seo, from 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, Dutch zee, German See, Swedish sjö), of unknown origin, outside connections "wholly doubtful" [Buck], and an IE etymon "has generally been doubted" [Boutkan]. The meaning "any great mass or large quantity" (of anything) is from c. 1200.

Germanic languages also use the more general Indo-European word (represented by English mere (n.1)) but have no firm distinction between "sea" and "lake," either large or small, by inland or open, salt or 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. The range in the Old English word included "the expanse of salt water that covers much of the world" to individual great, distinctly limited bodies of water; it also was used of inland seas, bogs, lakes, rivers, and the Bristol Channel.

The meaning "dark area of the moon's surface" is attested from 1660s (see mare (n.2)); before the invention of telescopes they were supposed to be water. The phrase sea change "transformation," literally "a change wrought by the sea," is attested from 1610, first in Shakespeare ("The Tempest," I.ii). Sea legs, humorous colloquial term implying ability to walk on a ship's deck when she is pitching or rolling is from 1712. At sea in the figurative sense of "perplexed" is attested from 1768, from literal sense (in reference to ships) of "out of sight of land" (c. 1300).

The sea, the most intact and ancient thing on the globe.

    Everything it touches is a ruin; everything it abandons is new.

[Paul Valéry, "Notebook" entry, 1921, transl. Nathaniel Brudavsky-Brody]

c. 1300, pouer, "ability; ability to act or do; strength, vigor, might," especially in battle; "efficacy; control, mastery, lordship, dominion, ability or right to command or control; legal power or authority; authorization; military force, an army," from Anglo-French pouair, Old French povoir, noun use of the infinitive, "to be able," earlier podir (9c.), from Vulgar Latin *potere (source also of Spanish poder, Italian potere), from Latin potis "powerful" (from PIE root *poti- "powerful; lord").

Whatever some hypocritical ministers of government may say about it, power is the greatest of all pleasures. It seems to me that only love can beat it, and love is a happy illness that can't be picked up as easily as a Ministry. [Stendhal "de l'Amour," 1822]

Meaning "one who has power, person in authority or exercising great influence in a community" is late 14c. Meaning "a specific ability or capacity" is from early 15c. In mechanics, "that with which work can be done," by 1727.

Sense of "property of an inanimate thing or agency of modifying other things" is by 1590s. Meaning "a state or nation with regard to international authority or influence" [OED] is from 1726. Meaning "energy available for work is from 1727. Sense of "electrical supply" is from 1896.

Colloquial a power of for "a large quantity of, a great number of" is from 1660s (compare powerful). Phrase the powers that be "the authorities concerned" is from Romans xiii.1. As a statement wishing good luck, more power to(someone) is recorded from 1842. A man-advantage power play in ice hockey so called by 1940. Power failure "failure of the (electrical) power supply" is from 1911; power steering in a motor vehicle is from 1921. Power politics "political action based on or backed by threats of force" (1937) translates German Macht-politik.