plimsoll

Etymology

From Samuel Plimsoll, a Bristol merchant.

noun

1. (Britain) A rubber-soled lace-up canvas shoe for sports or onboard ships; a precursor of trainers.
   “Yes, there are two distinct sets of footprints, both wearing rubber shoes—one I think ordinary plimsolls, the other goloshes,” replied the sergeant. 1928, Lawrence R. Bourne, chapter 13, in Well Tackled!
2. The plimsoll symbol ⦵ (or o) that is used as a superscript in the notation of thermodynamics to indicate an arbitrarily chosen non-zero reference point.