Green’s Dictionary of Slang

lavender, as sold in sachets.

1933		‘George Orwell’ Down and Out in Complete Works I (1986) 176: These (omitting the ones that everyone knows) are some of the cant words now used in London: [...] Funkum – lavender or other perfume sold in envelopes.
1936		W.A. Gape Half a Million Tramps 205: When it was cold we peddled ‘Funkum’. This is the tramps’ name for lavender.
1979		(con. 1920s) J. White ‘Campbell Bunk’ in History Workshop 17: In the early 1920s [...] He would exploit these verbal talents in selling ‘funkem’ [...] an innocuous mixture of lavender and bran in little envelopes which he’d sell door-to-door.