1620s, "make slippery or smooth" (especially by the application of an oil), from Latin lubricatus, past participle of lubricare "to make slippery or smooth," from lubricus "slippery; easily moved, sliding, gliding;" figuratively "uncertain, hazardous, dangerous; seductive," from suffixed form of PIE root *sleubh- "to slip, slide." Related: Lubricated; lubricating. Earlier verb was lubrify (early 15c.), from Medieval Latin lubrificare.
Proto-Indo-European root meaning "to slide, slip."
It forms all or part of: cowslip; lubric; lubricant; lubricate; lubricity; lubricous; sleeve; slip (n.3) "potter's clay;" sloop; slop (n.1) "semiliquid refuse;" slop (n.2) "loose outer garment;" sloven.
It is the hypothetical source of/evidence for its existence is provided by: Latin lubricus "slippery, slimy, smooth," lubricare "make slippery or smooth;" Middle Dutch slupen "to glide;" Gothic sliupan "to creep, slide;" Old English slyppe "dung."
"to smear or rub with oil or ointment," mid-15c., oilen, from oil (n.). Later especially "to lubricate (machinery)." Related: Oiled; oiling. An Old English verb in this sense was besmyrian.