Green’s Dictionary of Slang

1. a boaster.

1533		T. Elyot Of the knowledeg [sic] whiche maketh a wise man 90: PL. [W]oldest thou calle hym [a boastful tiler whose work is poor] than a good tylar or no? AR. Nay in good fayth, I wolde calle him but a prate.
1542		R. Burdet A dyalogue defensyue for women n.p.: A prater I am called, because I hyt the nayle / Euen vpon the heade, than sayde the Pye [i.e. magpie].
1550		J. Bale Apology xiii: Though Hierome wer a great prater & boaster of virginite, yet was he no virgine, but may be suspected of yl rule wt yōge womē.
1568		Hist. of Jacob and Esau V vi: What ye saucie merchaunt, are ye a prater now?
1572		S. Munster [trans.] Cosmographye 62: [H]ee was a prater and ful of wordes, bold, rashe, impudent, subtile, craftye.
1580		M. Cope [trans.] Prouerbes of Solomon 627: [T]hey shal suffer their senses to be blinded by some babler and prater, that knoweth cunningly how [...] to make his matter seeme good, the which is nothing worth.
1598		Tacitus [trans.] Annales 8: [A] common souldier; an impudent and saucy prater; well practised in disturbing assemblies.
1664		C. Cotton Virgil Travestie (1765) Bk I 28: And as thou art a cunning Prater, / Play me the fine Insinuator.
1756		W. Toldervy Hist. of the Two Orphans IV 91: Thus this prater begins, pray hear Humphry Copper!
1772		G. Stevens ‘Not As It Shou’d Be’ in Songs Comic and Satyrical 118: How many loud Coffee-house praters / Will boast of the weight / Which they have in the State. [Ibid.] ‘The Specific’ 162: Wine [...] At once turns a Mute to a Prater.

2. an itinerant, bogus preacher.

1674		Rochester ‘Tunbridge Wells’ in Works (1999) 49: I Trotted to the waters, / The Rendezvous of fools, Buffoons, and Praters.
1886		W. Newton Secrets of Tramp Life Revealed 22: We will now have a word with the tramp parsons. These travel in fours and fives. The head man calls himself the ‘Prater,’ or preacher. Their only object is to make money.