Origin and history of blatant

coined 1596 by Edmund Spenser in "The Faerie Queen," in blatant beast, a thousand-tongued monster representing slander; perhaps primarily an alliterative word, but perhaps suggested by Latin blatire "to babble." It entered general use by 1650s as "noisy in an offensive and vulgar way;" the sense of "obvious, glaringly conspicuous" is from 1889. Related: Blatantly; blatancy.

And therein were a thousand tongs empight

Of sundry kindes and sundry quality;

Some were of dogs that barked day and night,

And some of cats that wrawling still did cry,

And some of beares that groynd continually,

And some of tygres that did seeme to gren,

And snar at all that ever passed by ;

But most of them were tongues of mortall men,

Which spake reprochfully, not caring where nor when.

["Faerie Queene"]