Webster’s Revised Unabridged Dictionary · 1913
Spinach
Spin′ach, Spin′age, n. [OF. espinache, espinoche, F. épinard; cf. F. spinace, Sp. espinaca; all fr. Ar. isfānāj, isfināj, aspanākh, probably of Persian origin.] (Bot.) A common pot herb (Spinacia oleracea) belonging to the Goosefoot family.
Mountain spinach. See Garden orache, under Orache. — New Zealand spinach (Bot.), a coarse herb (Tetragonia expansa), a poor substitute for spinach.
☞ Various other pot herbs are locally called spinach.