Shady comes from shade plus the adjectival suffix -y; shade is from Old English sceadu ('shade, shadow'), from Proto-Germanic *skadwaz. The historical chain includes Old English sceadu and Proto-Germanic *skadwaz. The quoted older sense, "shade, shadow," supplies the immediate semantic anchor for shady. The formation is best read as suffixal and borrowed: the word shady carries its older form-history into a compact English lexical shape. In present English it is used as a adj, "giving shade, or of doubtful honesty or legality". English derivatives include shadily and shadiness; related English forms include shade and shadow. The result is a adj whose etymology preserves both the older form and the later English specialization.