early 15c., "act or process of becoming liquid," from French liquéfaction, from Late Latin liquefactionem (nominative liquefactio), noun of action from past-participle stem of Latin liquefacere "to make liquid, melt" (see liquefy). Formerly also used in a metaphysical sense, of the melting of the soul in the ardor of devotion. Related: Liquefacient.
Whenas in silks my Julia goes,
Then, then (methinks) how sweetly flows
That liquefaction of her clothes.
[Robert Herrick (1591-1647)]