mid-14c., zoþ ziggere (Kentish), "one who speaks truth,;" late 14c., sothseggere, "fortune-teller;" see sooth + say. Old English had soðsagu "act of speaking the truth."
sooth
soothe
soothfast
soothing
soothsay
soothsayer
sooty
sop
sopaipilla
soph
Sophia