O.E. læg, leag, from P.Gmc. *laugo (cf. M.Du. loghe, Du. loog, O.H.G. louga, Ger. Lauge "lye"), from PIE root *lou- "to wash" (see lave). The substance was used in the old days in place of soap, hence O.H.G. luhhen "to wash," O.N. laug "hot bath, hot spring," Dan. lørdag,
Swed. lördag "Saturday," lit. "washing-day." Chamber-lye in the Middle Ages was the name for urine used as a detergent.
lye (lī) Pronunciation Key
A strong alkaline solution or solid of potassium hydroxide or sodium hydroxide, made by allowing water to wash through wood ashes. It is used to make soap and drain and oven cleaners. Chemical formula:KOH or NaOH.