Etymology of "arse-smart" as a name for the water pepper

Question

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?

Answer 1

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):

Ἡγεμὼν είς τὰς γλῶσσας: Ductor in Linguas 544
Arsmart..because if it touch the taile or other bare skinne, it maketh it smart, as often it doth, being laid into the bed greene to kill fleas.

Answer 2

Wiktionary provides the following etymology:

Arse-smart

From arse +‎ smart, because the plant stings when it touches bare skin, and was often laid in beds to kill fleas.

(http://plants-of-styria.uni-graz.at/images/persicaria)