blither

The verb is a variant of blether (Northern England, Scotland), blather (“to say (something foolish or nonsensical); to say (something) in a foolish or overly verbose way; to babble (something); to talk rapidly without making much sense; to cry loudly, blubber”), from Middle English bloderen, blotheren (“to babble; to cry loudly, blubber”), from Old Norse blaðra (“to talk foolishly or inarticulately”), from blaðr (“nonsense”); further etymology uncertain.

The noun is a variant of blether, blather (“foolish or nonsensical talk”), either from blether, blather (verb), or from Old Norse blaðr (“nonsense”): see above.