underside

noun

Etymology: Etymology tree Proto-Indo-European *h₁én Proto-Indo-European *h₁entér Proto-Indo-European *(H)n̥dʰí Proto-Indo-European *-ér Proto-Indo-European *(H)n̥dʰér Proto-Germanic *under Proto-West Germanic *undar Old English under- Middle English under- English under- Proto-Indo-European *seh₁-der. Proto-Germanic *sīdaz Proto-Germanic *sīdǭ Old English sīde Middle English side English side English underside From under- + side.

1. The side that is below or underneath, the bottom.

   “A correspondent suggested that the superior riding qualities of the latter were due to the absence of piston-valve chests above the cylinders, which made it possible to bring the underside of the water-tanks to a lower level than that of the "Rivers", so minimising the unsteadying effect of water surging in the tanks.”

   “[...] and the neat reading lamps on the underside of the luggage racks, under passenger control, are an attractive feature of the first class compartments.”