>we should check OED, but W3 traces it from ME wetewold as in cokewold (cuckold).

OED2 not only supports this, but suggests a direct path from cokewold, and shows the second sense as transf. (? with pun on wit-all.) One who has little sense; a half-witted person; a fool; occas. a witling.
Shakespeare was an early user of the cuckold sense.