1868, variant of blether "talk nonsense" (1520s), a northern British and Scottish word (see blather (v.)). Related: Blithered; blithering.
Entries linking to blither
blather v.
"talk nonsense," 1520s, blether, Scottish, probably from a Scandinavian source such as Old Norse blaðra "mutter, wag the tongue," which is perhaps of imitative origin, or from Proto-Germanic *blodram "something inflated" (the source of bladder). Related: Blathered; blathering.
blithering adj.
1880, present-participle adjective (from the first typically with idiot) from blither (v.) "to talk nonsense." From 1872 as a verbal noun.