Today I learned that water pepper (Persicaria hydropiper, L. 1800) is otherwise called "arse-smart" in English:
PERSICARIA, Arse-smart
The Characters are;
It is a Plant with an apetalous Flower having several Stamina or Chives which arise from the multisid Calyx: the Pointal afterward becomes an oval-pointed smooth Seed, inclosed in the Capsule, which was before the Flower-cup: to which may be added, It hath jointed Stalks, and the Flowers are produced in Spikes.
—The Gardeners Dictionary (1754)
I failed to find its etymology in OED or other sources.
What could be the etymology of this name?
Best Answer
Arsesmart (variously spelled) is first attested in the OED around 1300, as ersmert, an alternative name for water pepper.
The origin is assumed to be simple composition, arse referring to a person's buttocks and smart in the verb sense of feeling pain, as asserted by John Minsheu in his 1617 Ductor in Linguas (Guide into Tongues):