so·da / ˈsōdə/ • n. 1. (also soda water or club soda) carbonated water (originally made with sodium bicarbonate) drunk alone or with liquor or wine: a whiskey and soda. ∎  (also soda pop) a carbonated soft drink: a can of soda.2. sodium carbonate, esp. as a natural mineral or as an industrial chemical. ∎  sodium in chemical combination: nitrate of soda.

soda Any of several sodium compounds, especially sodium carbonate (Na₂CO₃), usually manufactured from common salt (sodium chloride, NaCl) and ammonia by the Solvay process. The anhydrous (lacking water) form is known as soda ash; washing soda is hydrated sodium carbonate (Na₂CO₃.10H₂O)

soda sodium carbonate. XVI. — medL., perh. back-formation f. sodānum glasswort, based on Arab. ṣudā headache (for which the plant, containing soda, was used as a remedy), f. ṣada'a split.
Hence sodium (chem.) metal forming the base of soda. XIX.