Etymology: < post-classical Latin prunella (14th cent. in a glossary), perhaps alteration of brunella (15th cent. in a glossary, but compare the date of the Dutch below) < brunus (or one of its Germanic equivalents: see brown adj.) + classical Latin -ella -ella suffix, perhaps so called on account of its brownish purple sepals. The traditional derivation of the name from the plant's use to treat the disease prunella is probably a folk etymology, since this name for the disease is apparently first attested much later (see prunella n.²). Compare brunel n., prunel n.Compare Middle Dutch brunelle prunella (mid 14th cent.; Dutch bruinelle ), Middle Low German prūnellen prunella (rare), German Braunelle , historically denoting a variety of different plants, now usually in sense ‘prunella’ (mid 15th cent. as praunelle prunella); compare also Middle Low German brūnwort scrophularia, prunella, Middle High German brūnwurz baldmoney (German Braunwurz , historically denoting a variety of different plants, now usually in sense ‘scrophularia’ (see brownwort n.), in early modern German also ‘prunella’ (a1482)).

Etymology: < post-classical Latin prunella (1638 in the passage translated in quot. 1682 at sense 1), alteration (see below) of brunella (1599 or earlier) < brunus brown adj. + -ella -ella suffix; according to 16th-cent. writers, brunella was originally the Latin name of an infectious epidemic in the early 16th cent., which was called in German Bräune , perhaps diphteria (c1529; 14th cent. in general sense ‘brownness’), being so called because one of the symptoms associated with the disease was that the tongue was covered with a brown crust; compare jaundice n., and such names of diseases as whites (see white n. 14), yellows (see yellows n.), blues (see blue n. and compare blue disease n. at blue adj. and n. Compounds 1d), etc. Compare earlier brunel n., prunel n., prunella n.¹The reason for the alteration of post-classical Latin brunella to prunella is uncertain; it may perhaps have been due to German pronunciation, or perhaps to a later supposed etymology, taking it as a diminutive of classical Latin prūna ‘burning coal’ (see freeze v.). Kiliaan (1599) notes the following: ‘Bruyne..oris vitium cum linguæ tumore, exasperatione, siccitate, & nigredine: vnde et nomen teutonicè habet, vulgo brunella: quo nomine et herba vocatur quæ huic morbo medetur’, ‘Bruyne..an affliction of the mouth with swelling of the tongue, irritation, driness, and blackness: from which it also receives its German name, popularly brunella: which is also the name of the plant which is used to treat this illness’. In prunella salt at sense 2 after post-classical Latin sal prunellæ sal-prunella n. In prunella stone at sense 2 after post-classical Latin lapis prunellae (1627 or earlier).

Etymology: Probably a specific use of prunello n. (see forms at that entry), apparently with reference to the dark sloe-like colour of the fabric. Compare French prunelle dark-coloured light silk or worsted fabric (1779), and also Italian prunella (1908; < French prunelle).