Green’s Dictionary of Slang

1. (US black) traditional, tried and tested, long-established; also as adj.

1952		(con. 1948) G. Mandel Flee the Angry Strangers 249: She smoked enough for ten way-back Vipers.
1958		A. King Mine Enemy Grows Older (1959) 72: She had [...] become a complete mother. A mother from ’way back.

2. in a fig. far-away space, rather than time.

1963

E.J. Gaines ‘Just Like A Tree’ in King Black Short Story Anthol. (1972) 194: I mean these studs are ’way out. I mean like ’way back there.