late 14c., "pouring out of wine in honor of a god," from Latin libationem (nominative libatio) "a drink offering," noun of action from past participle stem of libare "pour out (an offering)," from PIE *(s)leib- "to pour, drop" (source of Greek leibein "to pour, make a libation"), an enlargement of root *lei- "to pour, to flow" (cognates: Sanskrit riyati "to let run;" Greek aleison "a wine vessel;" Lithuanian lieju "to pour," lytus "rain;" Hittite lilai- "to let go;" Albanian lyse, lise "a stream;" Welsh lliant "a stream, a sea," llifo "to flow;" Old Irish lie "a flood;" Breton livad "inundation;" Gaelic lighe "a flood, overflow;" Gothic leithu "fruit wine;" Old Church Slavonic liti, lêju, Bulgarian leja "I pour;" Czech liti, leji, Old Polish lić "to pour"). Transferred sense of "liquid poured out to be drunk" is from 1751. Related: Libations.