blackball v.

Old English blæc "absolutely dark, absorbing all light, of the color of soot or coal," from Proto-Germanic *blakaz "burned" (source also of Old Norse blakkr "dark," Old High German blah "black," Swedish bläck "ink," Dutch blaken "to burn"), from PIE *bhleg- "to burn, gleam, shine, flash" (source also of Greek phlegein "to burn, scorch," Latin flagrare "to blaze, glow, burn"), from root *bhel- (1) "to shine, flash, burn." The usual Old English word for "black" was sweart (see swart).

The same root produced Middle English blake "pale," from Old English blac "bright, shining, glittering, pale;" the connecting notions being, perhaps, "fire" (bright) and "burned" (dark), or perhaps "absence of color." According to OED, in Middle English "it is often doubtful whether blac, blak, blake, means 'black, dark,' or 'pale, colourless, wan, livid' "; and the surname Blake can mean either "one of pale complexion" or "one of dark complexion."  

Black was used of dark-skinned people in Old English. Of coffee with nothing added, attested by 1796. The meaning "fierce, terrible, wicked" is from late 14c. The figurative senses often come from the notion of "without light," moral or spiritual. Latin niger had many of the same figurative senses ("gloomy; unlucky; bad, wicked, malicious"). The metaphoric use of the Greek word, melas, however, tended to reflect the notion of "shrouded in darkness, overcast." In English it has been the color of sin and sorrow at least since c. 1300; the sense of "with dark purposes, malignant" emerged 1580s (in black art "necromancy;" it is also the sense in black magic). 

Black drop (1823) was a liquid preparation of opium, used medicinally. Black-fly (c. 1600) was a name given to various insects, especially an annoying pest of the northern American woods. Black Prince as a nickname of the eldest son of Edward III is attested by 1560s; the exact signification is uncertain. Black flag, flown (especially by pirates) as a signal of no mercy, is from 1590s. Black dog "melancholy" is attested from 1826.

Black belt is from 1870 in reference to district extending across the U.S. South with heaviest African population (also sometimes in reference to the fertility of the soil); it is attested from 1913 in the judo sense, worn by one who has attained a certain high degree of proficiency. Black power is from 1966, associated with Stokely Carmichael. Black English "English as spoken by African-Americans," is by 1969. The Black Panther (1965) movement was an outgrowth of Student Nonviolent Co-ordinating Committee. Black studies is attested from 1968.

"round object, compact spherical body," also "a ball used in a game," c. 1200, probably from an unrecorded Old English *beal, *beall (evidenced by the diminutive bealluc "testicle"), or from cognate Old Norse bollr "ball," from Proto-Germanic *balluz (source also of Dutch bal, Flemish bal, Old High German ballo, German Ball), from PIE root *bhel- (2) "to blow, swell."

The meaning "testicle" is from early 14c. (compare ballocks). Ball of the foot is from mid-14c. The meaning "rounded missile used in warfare" is from late 14c.

The meaning "a game played with a ball" is from mid-14c. The baseball sense of "pitch that does not cross the plate within the strike zone" is by 1889, probably short for high ball, low ball, etc.

Ball-point pen is by 1946. Ball of fire when first recorded in 1821 referred to "a glass of brandy;" as "spectacularly successful striver" it is attested from c. 1900. Many phrases are from sports: To have the ball "hold the advantage" is from c. 1400. To be on the ball is from 1912; to keep (one's) eye on the ball in the figurative sense is by 1907, probably ultimately on golf, where it was oft-repeated advice. Figurative use of ball in (someone's) court is by 1956, from tennis.

The head must necessarily be steady, for it is most important that you should keep your eye fixedly on the ball from the moment that the club-head is lifted from the ground until the ball is actually struck. "Keep your eye on the ball," should be your companion text to "Slow back." [Horace G. Hutchinson, "Hints on the Game of Golf," 1886]

Once a meeting is over, someone will be expected to do something. Make sure it is someone else. This is known as keeping the ball in their court. [Shepherd Mead, "How to Get Rich in TV Without Really Trying," 1956]