"bottom of anything considered as its support, foundation, pedestal," early 14c., from Old French bas "depth" (12c.), from Latin basis "foundation," from Greek basis "a stepping, a step, that on which one steps or stands, pedestal," from bainein "to go, walk, step" (from PIE root *gwa- "to go, come").
The military sense of "secure ground from which operations proceed" is attested from 1860. The chemical sense of "compound substance which unites with an acid to form a salt" (1810) was introduced in French 1754 by French chemist Guillaume-François Rouelle (1703-1770).
The sporting sense of "starting point" is from 1690s, also "destination of a runner" (1812). As a "safe" spot in a tag-like or ball game, it is suggested from mid-15c. (as the name of the game later called prisoner's base). Hence baseball, base-runner (1867), base-hit (1874), etc. The meaning "resources on which something draws for operation" (as in power-base, database, etc.) is by 1959.
1580s, transitive, "make or serve as a foundation for;" by 1841, of arguments, etc., "place (on or upon) a foundation," from base (n.). Related: Based; basing.
late 14c., "low, of little height," from Old French bas "low, lowly, mean," from Late Latin bassus "thick, stumpy, low" (used only as a cognomen in classical Latin, humilis being there the usual word for "low in stature or position"), possibly from Oscan, or Celtic, or related to Greek basson, comparative of bathys "deep."
The meaning "low on the social scale" is from late 15c.; that of "low in the moral scale" is attested by 1530s in English. The meaning "benefiting an inferior person or thing, unworthy" is from 1590s. Base metals (c. 1600) were worthless in contrast to noble or precious metals. Related: Basely.
early 12c., cnawlece "acknowledgment of a superior, honor, worship;" for the first element see know (v.). The second element is obscure, perhaps from Scandinavian and cognate with the -lock "action, process," found in wedlock.
From late 14c. as "capacity for knowing, understanding; familiarity;" also "fact or condition of knowing, awareness of a fact;" also "news, notice, information; learning; organized body of facts or teachings." The sense of "sexual intercourse" is from c. 1400. Middle English also had a verb form, knoulechen "acknowledge" (c. 1200), later "find out about; recognize," and "to have sexual intercourse with" (c. 1300); compare acknowledge.
Since Knowledge is but sorrow's Spy,
It is not safe to know.
[Davenant, song from "The Just Italian," 1630]
"possessing knowledge of all things, having universal knowledge," c. 1600, from Modern Latin omniscientem (nominative omnisciens) "all-knowing," a back-formation from Medieval Latin omniscientia "all-knowledge," from Latin omnis "all" (see omni-) + scientia "knowledge" (see science). Related: Omnisciently.
"the refuse matter which passes through sewers," 1818, probably from the apparent base of sewer (n.1) + -age. There was a verb sew "to drain, to draw off water," attested from late 15c., but by 19c. it seems to have survived only in provincial dialect, and OED writes, "It was prob. framed without any knowledge of the verb as having been actually used." Compare sewerage.