late Old English sparage, from Latin asparagus (in Medieval Latin often sparagus), from Greek asparagos, of uncertain origin; probably from PIE root *sp(h)er(e)g- "to spring up" (though perhaps from a non-Greek source). In Middle English, asperages sometimes was regarded as a plural, with false singular aspergy.
By 16c. the word had been anglicized as far as sperach, sperage. It was respelled by c.1600 to conform with classical Latin, but then folk-etymologized formation sparrowgrass arose 17c., persisting into 19c., during which time asparagus had "an air of stiffness and pedantry" [John Walker, "Critical Pronouncing Dictionary," 1791]. Known in Old English as eorðnafela.