rainmaker (n.)

Middle English rein, from Old English regn "rain, descent of water in drops through the atmosphere," from Proto-Germanic *regna- (source also of Old Saxon regan, Old Frisian rein, Middle Dutch reghen, Dutch regen, German regen, Old Norse regn, Gothic rign "rain"), with no certain cognates outside Germanic, unless it is from a presumed PIE *reg- "moist, wet," which may be the source of Latin rigare "to wet, moisten" (see irrigate).

Rain dance "dance performed by a tribal group in hope of summoning rain" is from 1867; rain date in listings for outdoor events, giving an alternative date should rain interrupt them on the intended day, is from 1948. To know enough to come in out of the rain (usually with a negative) "take ordinary measures for one's protection" is from 1590s. Rain-shower is Old English renscur. Rain-gauge "instrument for collecting and measuring the amount of rainfall at a given place" is by 1769.

Old English macian "to give being to, give form or character to, bring into existence; construct, do, be the author of, produce; prepare, arrange, cause; behave, fare, transform," from West Germanic *makōjanan "to fashion, fit" (source also of Old Saxon makon, Old Frisian makia "to build, make," Middle Dutch and Dutch maken, Old High German mahhon "to construct, make," German machen "to make"), from PIE root *mag- "to knead, fashion, fit." If so, sense evolution perhaps is via prehistoric houses built of mud. It gradually replaced the main Old English word, gewyrcan (see work (v.)).

Meaning "to arrive at" (a place), first attested 1620s, originally was nautical. Formerly used in many places where specific verbs now are used, such as to make Latin (c. 1500) "to write Latin compositions." This broader usage survives in some phrases, such as make water "to urinate" (c. 1400), make a book "arrange a series of bets" (1828), make hay "to turn over mown grass to expose it to sun." Make the grade is 1912, perhaps from the notion of railway engines going up an incline.

Read the valuable suggestions in Dr. C.V. Mosby's book — be prepared to surmount obstacles before you encounter them — equipped with the power to "make the grade" in life's climb. [advertisement for "Making the Grade," December 1916]

But the phrase also was in use in a schoolwork context at the time.

To make friends is from late 14c.; to make good "make right" is from early 15c.  To make do "manage with what is available" is attested by 1867; to make for "direct one's course to, proceed toward" is from 1580s, but "Not frequent before the 19th c." [OED]. To make of  "think, judge" is from c. 1300. To make off  "run away, depart suddenly" is from 1709; to make off with "run away with (something) in one's possession" is by 1820. To make way is from c. 1200 as "cut a path," early 14c. as "proceed, go."

Make time "go fast" is 1849; make tracks in this sense is from 1834. To make a federal case out of  (something) was popularized in 1959 movie "Anatomy of a Murder;" to make an offer (one) can't refuse is from Mario Puzo's 1969 novel "The Godfather." To make (one's) day is by 1909; menacing make my day is from 1971, popularized by Clint Eastwood in film "Sudden Impact" (1983). Related: Made; making.