c.1200, "stupid;" early 13c., "blunt, not sharp;" rare before mid-14c., apparently from Old English dol "dull-witted, foolish," or an unrecorded parallel word, or from Middle Low German dul "slow-witted," both from Proto-Germanic *dulaz (cf. Old Frisian and Old Saxon dol "foolish," Old High German tol, German toll "mad, wild," Gothic dwals "foolish"), from PIE *dheu- (1) "dust, vapor, smoke" (and related notions of "defective perception or wits"). Of color from early 15c.; of pain or other sensations from 1725. Sense of "boring" first recorded 1580s.
dull. (8) Not exhilarating; not delightful; as to make dictionaries is dull work. [Johnson]Dullsville, slang for "town where nothing happens," attested from 1960.
c.1200, "to grow weary, tire;" of pointed or edged things from c.1400; of the senses from 1550s; from dull (adj.). Related: Dulled; dulling.
adj. dull·er, dull·est
Lacking responsiveness or alertness; insensitive.
Not intensely or keenly felt, as in pain.