"uncertain as to specifics," 1540s, from Middle French vague "empty, vacant; wild, uncultivated; wandering" (13c.), from Latin vagus "strolling, wandering, rambling," figuratively "vacillating, uncertain," perhaps from PIE *Huog-o-  and cognate with Old Norse vakka "to stray, hover," Old High German wankon "to totter, stagger," Old High German winkan "to waver, stagger, wink," Old English wincian "to nod" [de Vaan]. Related: Vagueness.

river-land between two ranges of hills, early 14c., from Old French val "valley, vale" (12c.), from Latin vallem (nominative vallis, valles) "valley" (see valley). Now "little used except in poetry" [Century Dictionary]. Vale of years "old age" is from "Othello." Vale of tears "this world as a place of trouble" is attested from 1550s. An older phrase in the same sense was dale of dol (mid-15c.).