What is the X in X-mas?
"small body of water," Old English pol "small body of water; deep, still place in a river," from West Germanic *pol- (cf. Old Frisian and Middle Low German pol, Dutch poel, Old High German pfuol, German Pfuhl). As a short form of swimming pool it is recorded from 1901. Pool party is from 1965.
game similar to billiards, 1848, originally (1690s) a card game played for collective stakes (a "pool"), from French poule "stakes, booty, plunder," literally "hen," from Old French poille "hen, young fowl" (see foal (n.)).
Perhaps the original notion is from jeu de la poule, supposedly a game in which people threw things at a chicken and the player who hit it, won it, which speaks volumes about life in the Middle Ages. The notion behind the word, then, is "playing for money." The connection of "hen" and "stakes" is also present in Spanish polla and Walloon paie.
Meaning "collective stakes" in betting first recorded 1869; sense of "common reservoir of resources" is from 1917. Meaning "group of persons who share duties or skills" is from 1928. From 1933 as short for football pool in wagering. Pool shark is from 1898. The phrase dirty pool "underhanded or unsportsmanlike conduct," especially in politics (1951), seems to belong here now, but the phrase dirty pool of politics, with an image of pool (n.1) is recorded from 1871 and was in use early 20c.
"to make a common interest, put things into a pool," 1871, from pool (n.2). Related: Pooled; pooling.
of liquid, "to form a pool or pools," 1620s, from pool (n.1).
A collection of blood in any region of the body due to dilation and retardation of the circulation in capillaries and veins.
a pond, or reservoir, for holding water (Heb. berekhah; modern Arabic, birket), an artificial cistern or tank. Mention is made of the pool of Gibeon (2 Sam. 2:13); the pool of Hebron (4:12); the upper pool at Jerusalem (2 Kings 18:17; 20:20); the pool of Samaria (1 Kings 22:38); the king's pool (Neh. 2:14); the pool of Siloah (Neh. 3:15; Eccles. 2:6); the fishpools of Heshbon (Cant. 7:4); the "lower pool," and the "old pool" (Isa. 22:9,11). The "pool of Bethesda" (John 5:2,4, 7) and the "pool of Siloam" (John 9:7, 11) are also mentioned. Isaiah (35:7) says, "The parched ground shall become a pool." This is rendered in the Revised Version "glowing sand," etc. (marg., "the mirage," etc.). The Arabs call the mirage "serab," plainly the same as the Hebrew word _sarab_, here rendered "parched ground." "The mirage shall become a pool", i.e., the mock-lake of the burning desert shall become a real lake, "the pledge of refreshment and joy." The "pools" spoken of in Isa. 14:23 are the marshes caused by the ruin of the canals of the Euphrates in the neighbourhood of Babylon. The cisterns or pools of the Holy City are for the most part excavations beneath the surface. Such are the vast cisterns in the temple hill that have recently been discovered by the engineers of the Palestine Exploration Fund. These underground caverns are about thirty-five in number, and are capable of storing about ten million gallons of water. They are connected with one another by passages and tunnels.