"affording shade," 1570s; "protected by shade," 1590s; from shade (n.) + -y (2). Meaning "disreputable" (1862) probably is from earlier university slang sense of "of questionable merit, unreliable" (1848). Related: Shadily; shadiness. Old English had sceadlic "shady, 'shadely.'"
her shady past intrigued him
a shady part of town
a shady deal
He established a dummy company through which he laundered vast sums of cash from shady middlemen and arms dealers
the shady side of the street
shadow-figure
shadowland
shadowless
shadowy
Shadrach
shady
Shafi'i
shaft
shag
shagbark
shaggy