Green’s Dictionary of Slang

blither n.

nonsense.

1901		Daily Chronicle (London) 10 Aug. 4/7: We have heard a lot of blither (and, perhaps, a little sense).
1910		‘Doss Chiderdoss’ ‘Guid Advice’ Sporting Times 2 July 1/3: Although to chaff the lassies I rejoice, / There’s nae harm in it, there’s nae love-making blither in the case.
1911		E. Ferber Dawn O’Hara (1925) 64: What utter blither!