sole (n.1) Look up sole at Dictionary.com
"bottom of the foot," early 14c., from O.Fr. sole, from L. solea "sandal, bottom of a shoe," from solum "bottom, ground, soil," of unknown origin. The verb meaning "to provide with a sole" is recorded from 1560s.
sole (adj.) Look up sole at Dictionary.com
"single," late 14c., from O.Fr. soul (fem. soule), from L. solus "alone," of unknown origin, perhaps related to se "oneself," from PIE reflexive base *swo- (see so).
sole (n.2) Look up sole at Dictionary.com
"flatfish," mid-13c., from O.Fr. sole, from L. solea "a kind of flatfish," originally "sandal" (see sole (n.1)), so called from resemblance of the fish to a sandal.