"The successful applicant will have a N.E.W.T. in Potions"
-- recruitment advertisement in the Daily Prophet (DP2)
Madam Pimpernelle was a witch who had a beauty shop in Diagon Alley (DP2)
Madam Primpernelle produced a line of Beautifying Potions from her shop at 275 Diagon Alley. She advertised in the Daily Prophet for a Junior Potion mixer who could cope with wart removal and other beauty treatments (DP2)
To "primp" means on to make yourself beautiful, generally in front of a mirror. The "....elle" ending gives her name a French flavour and, as everyone knows, French women (particularly in Paris) have a reputation for good style and grooming.
A pimpernel is a type of flower.
In the novel The Scarlet Pimpernel by Baroness Emma Orczy, a foppish Englishman named Sir Percy Blakeney assumes the identity of the Scarlet Pimpernel when he uses masterful disguises to rescue French aristocrats from the Reign of Terror.