Earlier references, such as in Jane Austen's "Northanger Abbey," refer to the game of rounders, (baseball is a more elaborate variety of it). The modern game was legendarily invented 1839 by Abner Doubleday in Cooperstown, N.Y. Base was used for "start or finish line of a race" from 1690s; and the sense of "safe spot" found in modern children's game of tag can be traced to 15c. (the use in reference to the bags in modern baseball is from 1868). Baseball as "ball with which the game of baseball is played" is by 1885.
mid-14c., diamaunt, diamond, "extremely hard and refractive precious stone made of pure or nearly pure carbon," from Old French diamant, from Medieval Latin diamantem (nominative diamas), from Vulgar Latin *adiamantem (which was subsequently altered by influence of the many Greek words in dia-), from Latin adamantem (nominative adamans) "the hardest metal," later, "diamond," from Greek adamas (genitive adamantos), name of a hypothetical hardest material, noun use of an adjective meaning "unbreakable, inflexible," a word of uncertain origin (see adamant (n.)).
From early 15c. as "person of great worth" (a sense also in Latin). From late 15c. as "geometric figure of four equal straight lines forming two acute and two obtuse angles." From 1590s as "playing-card stamped with one or more red diamonds." In baseball, "square space enclosed within the four bases," is American English, by 1875. As an adjective "resembling, consisting of, or set with diamonds," from 1550s.
"powdered glass or crystal," by 1904, from French diamanté, past participle of diamanter "to set with diamonds," from Old French diamant (see diamond). Diamante also was a Middle English form of diamond.
c. 1200, "broken ground, a rough surface," from rough (adj.). From 1640s as "the disagreeable side of anything." The meaning "a rowdy" is attested by 1837, but Century Dictionary calls this perhaps rather an abbreviation of ruffian conformed in spelling to rough. The specific sense in golf, in reference to the ground at the edge of the greens, is by 1901.
Phrase in the rough "in an unfinished or unprocessed condition" (of timber, etc.) is from 1620s, in rough diamond "diamond in its natural state," which was used figuratively, of persons, by 1700, hence diamond in the rough (by 1874 of persons, in the figurative sense "one whose good character is somewhat masked by rough manners and want of education or style").
famous diamond, one of the British crown jewels after the annexation of Punjab in 1849, from Persian koh-i-nur, literally "mountain of light," from Persian koh "mountain" + Arabic nur "light."
"waste diamonds, small chips from diamond-cutting," 1620s, a word of unknown origin, perhaps related to Old French bort "bastard."
measure of quality of a diamond, c. 1600, from water (n.1), perhaps as a translation of Arabic ma' "water," which also is used in the sense "luster, splendor."