back of one's mind

Noun

back of one's mind

1. One's remote memory.
   • It was authorised by an Act of May 5, 1837, and, although the estimates of its future prosperity were based on traffic already passing between the two towns, it seems likely that, even in 1837, the promoters had the possible extension of the railway system into Scotland at the back of their minds.1960 February, M. D. Greville and G. O. Holt, “Railway Development in Preston—1”, in Railway Magazine, page 96
   • So much of what followed from the drawing boards of others will have been designed with the demands, effort and grandeur of Primrose Hill [tunnel] in the back of their minds.2020 August 26, Tim Dunn, “Great railway bores of our time!”, in Rail, page 44
2. The supposed location of low-importance plans within the brain.
   • Wallpapering the bedroom has been at the back of my mind for some time now.
   • In the backs of all our minds was the proud hope that somehow or other we should get there.2008, Major General John Frost, A Drop Too Many