sand-hill n.

"water-worn detritus finer than gravel; fine particles of rocks (largely crystalline rocks, especially quartz); the material of the beach, desert, or sea-bed;" Old English sand, from Proto-Germanic *sandam (source also of Old Norse sandr, Old Frisian sond, Middle Dutch sant, Dutch zand, German Sand), from PIE *bhs-amadho- (source also of Greek psammos "sand;" Latin sabulum "coarse sand," which is the source of Italian sabbia, French sable), suffixed form of root *bhes- "to rub."

Historically, the line between sand and gravel cannot be distinctly drawn. Used figuratively in Old English in reference to innumerability and instability. General Germanic, but not attested in Gothic, which used in this sense malma, related to Old High German melm "dust," the first element of the Swedish city name Malmö (the second element meaning "island"), and to Latin molere "to grind."

Metaphoric for innumerability since Old English. In compounds, often indicating "of the shore, found on sandy beaches." In old U.S. colloquial use, "grit, endurance, pluck" (1867), especially in have sand in (one's) craw. Sands "tract or region composed of sand," is by mid-15c.

Old English hyll "hill," from Proto-Germanic *hulni- (source also of Middle Dutch hille, Low German hull "hill," Old Norse hallr "stone," Gothic hallus "rock," Old Norse holmr "islet in a bay," Old English holm "rising land, island"), from PIE root *kel- (2) "to be prominent; hill." Formerly including mountains.

In Great Britain heights under 2,000 feet are generally called hills; 'mountain' being confined to the greater elevations of the Lake District, of North Wales, and of the Scottish Highlands; but, in India, ranges of 5,000 and even 10,000 feet are commonly called 'hills,' in contrast with the Himalaya Mountains, many peaks of which rise beyond 20,000 feet. [OED]

The term mountain is very loosely used. It commonly means any unusual elevation. In New England and central New York, elevations of from one to two thousand feet are called hills, but on the plains of Texas, a hill of a few hundred feet is called a mountain. [Ralph S. Tarr, "Elementary Geology," Macmillan, 1903]

Despite the differences in defining mountain systems, Penck (1896), Supan (1911) and Obst (1914) agreed that the distinction between hills, mountains, and mountain systems according to areal extent or height is not a suitable classification. ["Geographic Information Science and Mountain Geomorphology," 2004]

 Figurative phrase over the hill "past one's prime" is recorded by 1950. Expression old as the hills is recorded by 1819, perhaps echoing Job xv.7. Earlier form old as the hills and the valleys is attested by 1808:

And this is no "new morality." It is morality as old as the hills and the valleys. It is a morality which must be adopted; or, we must confess that there are certain political evils greater than that of seeing one's country conquered. [Cobbett's Weekly Political Register, Feb. 6, 1808]

Cobbett's also had, on April 11, 1818:

However, thus it always is: "those whom God intends to destroy, he first makes foolish," which is a saying as old as the hills between Everly and Marlborough.

mid-15c., "hard wafer," literally "that which cracks or breaks," agent noun from crack (v.). The specific application to a thin, hard or crisp biscuit is by 1739, mostly in American English; the meaning "instrument for crushing or cracking" is from 1630s (compare nut-cracker).

Coal-cracker is from 1853 of persons, 1857 of machinery that breaks up mined coal. The cracker-barrel (1861) full of soda-crackers for sale was such a common feature in the popular perception of country stores that the phrase came to be used by 1905 as an adjective, "emblematic of down-home ways and views."