Old English grund "bottom; foundation; surface of the earth," also "abyss, Hell," and "bottom of the sea" (a sense preserved in run aground), from Proto-Germanic *grundu-, which seems to have meant "deep place" (source also of Old Frisian, Old Saxon, Danish, Swedish grund, Dutch grond, Old High German grunt, German Grund "ground, soil, bottom;" Old Norse grunn "a shallow place," grund "field, plain," grunnr "bottom"). No known cognates outside Germanic.
Sense of "reason, motive" first attested c. 1200. Meaning "source, origin, cause" is from c. 1400. Electrical sense "connection with the earth" is from 1870 (in telegraphy). Meaning "place where one takes position" is from 1610s; hence stand (one's) ground (1707). To run to ground in fox-hunting is from 1779. Ground rule (1890) originally was a rule designed for a specific playing field (ground or grounds in this sense attested by 1718); by 1953 it had come to mean "a basic rule."
mid-13c., "to put on the ground, to strike down to the ground;" late 14c., "lay the foundation of," also, figuratively, "to base" (an argument, sermon, etc.), from ground (n.). Meaning "instruct thoroughly in the basics" is from late 14c. Of ships, "to run into the ground," from mid-15c. (intransitive), transitive sense from 1650s. Of arms, from 1711. Electrical sense from 1881. Meaning "deny privileges" is 1940s, originally a punishment meted out to pilots (in which sense it is attested from 1930). In the sense "establish firmly" Old English had grundweallian, grundstaðelian; also gryndan "descend," gegryndan "to found."
"reduced to fine particles by grinding," 1765, past-participle adjective from grind (v.).