Green’s Dictionary of Slang

to act in a slovenly manner.

1875		Leicester Chron. 6 Mar. 5/2: Slammacking — Awkward; clumsy; blundering.
1888–94		‘Walter’ My Secret Life (1966) III 612: I’ll take them [i.e. petticoats] off, I can slammack about to-night, — no one will see me.