Green’s Dictionary of Slang

very drunk, also as adv.

1889		Sunderland Dly Echo 18 Nov. 3/2: he came home at might ‘mortallius,’ four companions [...] singing and shouting a drunken song.
1889		Sunderland Dly Echo 20 Sept. 3/1: She used to lie in bed through the day, and at night go out and get ‘mortallious’.
1903		Morpeth Herald 28 Feb. 2/4: We are expected to get so mortallious on Saturday that we cannot raise a head [...] until the pub opens on Monday.
1905		Morpeth Herald 22 Apr. 6/7: He was drunk, ‘mortallious’ drunk.