Liquid
late Middle English: from Latin liquidus, from liquere ‘be liquid’.
wiktionary
From Middle English liquide, from Old French liquide, from Latin liquidus(“fluid, liquid, moist”), from liqueō(“to be liquid, be fluid”), ultimately from Proto-Indo-European *wleykʷ-(“to flow, run”). Doublet of liquidus. As a term for a consonant, it comes from Latin liquida ( cōnsōnāns), a calque of Ancient Greek ὑγρὸν ( σύμφωνον)(hugròn (súmphōnon), “liquid consonant”).
etymonline
liquid (adj.)
late 14c., "flowing, capable of flowing; neither solid nor gaseous," from Old French liquide "liquid, running" (13c.), from Latin liquidus "fluid, liquid, moist," figuratively "flowing, continuing," also of sounds and voices, from liquere "be fluid," related to liqui "to melt, flow," from PIE *wleik- "to flow, run."
In English, of sounds from 1630s. Financial sense of "capable of being converted to cash" is first recorded 1818, from earlier use in Scots Law (17c.) in reference to debts that had been proved (in court, etc.).
liquid (n.)
"a liquid substance," 1708, from liquid (adj.). Earlier it meant "sound of a liquid consonant" (1520s), following Latin liquidae, Greek hygra, applied to letters of an easy, "flowing" sound.
