Green’s Dictionary of Slang

very, extremely, completely.

1836		T. Haliburton Clockmaker I 191: I had no business to run an old roadster so everlastin fast.
1843		W. Oliver Eight Months in Illinois 66: The old doctor was so everlastin’ busy.
1847		J. Downey Cruise of the Portsmouth (1963) 94: These ’ere natives are too ever-lasting lazy to catch ’em.
1860		T. Haliburton Season Ticket 250: I can’t talk book learnin’ [...] nor eberlastin’ long words.
1900		Boy’s Own Paper 24 Nov. 116: Hurd was standing outside his door smoking his everlasting short pipe.
1908		A.N. Lyons Arthur’s 301: You everlastin’ ole box of tricks, you.