Green’s Dictionary of Slang

(UK Und.) to run off.

1842		Egan ‘The Bridle Cull’ in Farmer Musa Pedestris (1896) 139: ‘I’ll not rob you,’ said he, ‘and so you needn’t bunk;’ / But she lammas’d off in style, of his pop-gun afunk.
1853		Tasmanian Colonist 19 Sept. 2/4: Mary Nugent struck him on the head with her fist: as soon as she did so, King said to her, ‘lammas’ a slang term for ‘be off’.
1866		Wild Boys of London I 86/1: ‘I mizzled.’ ‘Eh?’ ‘Sloped.’ ‘What was that?’ ‘Lammassed, don’t yer know.’ ‘How strangely you talk.’ ‘It’s the gipsies’ delerict.’ [...] ‘The gipsies what?’ ‘Lingo.’.