c. 1746, also in early use gaumless, gawmless, "wanting sense, stupid," a British dialectal word, from gome "notice, understanding" (c. 1200), from Old Norse gaumr "care, heed" (of unknown origin); + -less.
Entries linking to gormless
-less
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.