= a dark area or shape produced by an object coming between the rays of the sun and a surface, which provides shelter and respite from the sun's heat, and can also be used as a means of measuring time; associated with safety and protection, but also with things that are fleeting and will vanish in time

literally: shadow; hence: = state in which humans are safe from danger, in the same way as as shaded place provides safety from the heat of the sun