Old English wull, from Proto-Germanic *wulno (cf. Old Norse ull, Old Frisian wolle, Middle Dutch wolle, Dutch wol, Old High German wolla, German wolle, Gothic wulla), from PIE *wele- (cf. Sanskrit urna; Avestan varena; Greek lenos "wool;" Latin lana "wool," vellus "fleece;" Old Church Slavonic vluna, Russian vulna, Lithuanian vilna "wool;" Middle Irish olann, Welsh gwlan "wool"). Figurative expression pull the wool over (someone's) eyes is recorded from 1839, American English.
To deceive; mislead: The whole indignant act was an attempt to pull the wool over the voters' eyes
[1842+; a slightly earlier form is spread the wool over someone's eyes]