"level of saturated ground," 1879, from water (n.1) + table (n.).
Entries linking to water-table
water n.1
Old English wæter, from Proto-Germanic *watr- (source also of Old Saxon watar, Old Frisian wetir, Dutch water, Old High German wazzar, German Wasser, Old Norse vatn, Gothic wato "water"), from PIE *wod-or, suffixed form of root *wed- (1) "water; wet."
To keep (one's) head above water in the figurative sense is recorded from 1742. Water cooler is recorded from 1846; water polo from 1884; water torture from 1928. Linguists believe PIE had two root words for water: *ap- and *wed-. The first (preserved in Sanskrit apah as well as Punjab and julep) was "animate," referring to water as a living force; the latter referred to it as an inanimate substance. The same probably was true of fire (n.).
table n.
late 12c., "board, slab, plate," from Old French table "board, square panel, plank; writing table; picture; food, fare" (11c.), and late Old English tabele "writing tablet, gaming table," from Germanic *tabal (source also of Dutch tafel, Danish tavle, Old High German zabel "board, plank," German Tafel). Both the French and Germanic words are from Latin tabula "a board, plank; writing table; list, schedule; picture, painted panel," originally "small flat slab or piece" usually for inscriptions or for games (source also of Spanish tabla, Italian tavola), of uncertain origin, related to Umbrian tafle "on the board."
The sense of "piece of furniture with the flat top and legs" first recorded c. 1300 (the usual Latin word for this was mensa (see mensa); Old English writers used bord (see board (n.1)). Especially the table at which people eat, hence "food placed upon a table" (c. 1400 in English). The meaning "arrangement of numbers or other figures on a tabular surface for convenience" is recorded from late 14c. (as in table of contents, mid-15c.).
Figurative phrase turn the tables (1630s) is from backgammon (in Old and Middle English the game was called tables). Table talk "familiar conversation around a table" is attested from 1560s, translating Latin colloquia mensalis. Table manners is from 1824. Table-hopping is recorded by 1943. The adjectival phrase under-the-table "hidden from view" is recorded from 1949; to be under the table "passed out from excess drinking" is recorded from 1913. Table tennis "ping-pong" is recorded from 1887. Table-rapping in spiritualism, supposedly an effect of supernatural powers, is from 1853.