Webster's Revised Unabridged Dictionary · 1913

Lye

Lye , noun

[Anglo-Saxon leáh; akin to Dutch loog, Old High German louga, German lauge; compare Icelandic laug a bath, a hot spring.]

1.
A strong caustic alkaline solution of potassium salts, obtained by leaching wood ashes. It is much used in making soap, etc.
2.
(Chemistry) Sodium hydroxide or potassium hydroxide, or a concentrated aqueous solution of either compound.

Lye , noun

(Railroad) A short side line, connected with the main line; a turn-out; a siding. [English]

Lye , noun

A falsehood. [Obsolete]