make-believe n.

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.

Middle English bileven, from Old English belyfan "to have faith or confidence" (in a person), earlier geleafa (Mercian), gelefa (Northumbrian), gelyfan (West Saxon), from Proto-Germanic *ga-laubjan "to believe," perhaps literally "hold dear (or valuable, or satisfactory), to love" (source also of Old Saxon gilobian "believe," Dutch geloven, Old High German gilouben, German glauben), ultimately a compound based on PIE root *leubh- "to care, desire, love" (see belief).

The meaning "be persuaded of the truth of" (a doctrine, system, religion, etc.) is from mid-13c.; the meaning "credit upon the grounds of authority or testimony without complete demonstration, accept as true" is from early 14c. The general sense of "be of the opinion, think" is from c. 1300. Related: Believed (formerly occasionally beleft); believing.

The form beleeve was common till 17c., the spelling then changed, perhaps by influence of relieve, etc. To believe on instead of in was more common in 16c. but now is a peculiarity of theology; believe of also sometimes was used in 17c. The expression believe it or not is attested by 1874; Robert Ripley's newspaper cartoon of the same name is from 1918. Emphatic you better believe attested from 1854.