1660s, "body fluid," from Latin latex (genitive laticis) "liquid, a liquid, fluid," probably from Greek latax "dregs," from PIE root *lat- "wet, moist" (source also of Middle Irish laith "beer," Welsh llaid "mud, mire," Lithuanian latakas "pool, puddle," Old Norse leþja "filth").
From 1835 as "milky liquid from plants." Meaning "water-dispersed polymer particles" (used in rubber goods, paints, etc.) is from 1937. As an adjective by 1954, in place of the classically correct laticiferous.
1791, in chemistry, "liquefying in air," from Latin deliquescentem (nominative deliquescens), present participle of deliquescere "to melt away," from de- (see de-) + liquescere "to melt," from liquere "to be liquid" (see liquid (adj.)). Transferred or figurative sense of "apt to dissolve or melt away" is by 1837. Related: Deliquescence.
c. 1600, from French limpide (15c.) and directly from Latin limpidus "clear, transparent" (source also of Spanish límpido, Italian limpido), related to limpor "a clear liquid," limpa "water goddess, water," which is perhaps cognate with lympha "clear liquid" (see lymph). Related: Limpidly.
1670s, "watery animal fluid," especially the clear pale-yellow liquid which separates in coagulation of blood in wounds, etc., from Latin serum "watery fluid, whey." This is held to be from PIE *sero- "flowing, liquid," from verbal root *ser- "to run, flow" (source also of Greek oros "whey, watery parts of curdled milk;" Sanskrit sarah "flowing, liquid," sarit "brook, river"). The word was applied by 1893 to blood serum used in medical treatments.
Old English socian (intransitive) "to soak, to lie in liquid," from Proto-Germanic *sukon (source also of West Flemish soken), possibly from PIE *sug-, from root *seue- (2) "to take liquid" (see sup (v.2)). Transitive sense "drench, permeate thoroughly" is from mid-14c.; that of "cause to lie in liquid" is from early 15c. Meaning "take up by absorption" is from 1550s. Slang meaning "to overcharge" first recorded 1895. Related: Soaked; soaking. As a noun, mid-15c., from the verb.