c. 1400, "one who establishes," agent noun from ground (v.). Baseball sense attested by 1867; earlier in cricket.
Entries linking to grounder
ground v.
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."