guileless (adj.)

mid-12c., from Old French guile "deceit, wile, fraud, ruse, trickery," probably from Frankish *wigila "trick, ruse" or a related Germanic source, from Proto-Germanic *wih-l- (source also of Old Frisian wigila "sorcery, witchcraft," Old English wig "idol," Gothic weihs "holy," German weihen "consecrate"), from PIE root *weik- (2) "consecrated, holy."

word-forming element meaning "lacking, cannot be, does not," from Old English -leas, from leas "free (from), devoid (of), false, feigned," from Proto-Germanic *lausaz (cognates: Dutch -loos, German -los "-less," Old Norse lauss "loose, free, vacant, dissolute," Middle Dutch los, German los "loose, free," Gothic laus "empty, vain"), from PIE root *leu- "to loosen, divide, cut apart." Related to loose and lease.