Green’s Dictionary of Slang

a chatterer, a gossip.

1673		Wycherley Gentleman Dancing-Master I i: Y fackins; but you shan’t ask him, if you go there to look you, you Prattle-box you, I’le ask him.
1698		N. Ward London Spy II 38: How do I know that, Mr. Prattle-box?
1707		Humours of a Coffee-House 20 Aug. 8: I wish the Furies had the Clawing of that Impertinent Prattle-Box.
1707		N. Ward London Terraefilius IV 36: She is an invidious Tattle-box, that Rattles People out of their Senses.
1751		R.S. Life and Adventures of Peter Wilkins I 11: At last, the old Prattlebox [...] made a short Pause, to recover Breath.
1771		R. King New London Spy 136: [A] rattle-headed prattle box.
1782		Scots Mag. 1 Feb. 99/2: ‘A rhapsodist [...] is like you, my dear, a prattle-box’.
1851		Advocate (Dublin) 21 May 10/1: ‘Hold your tongue, you prattle-box’.
1854		London Standard 8 Mar. 2/3: These prayers will be somewhat more vitalising than those pattered [...] by the disciples of Father Ignatius Gra-mercy Gad-about Prattle-box Spencer.
1899		Dublin Wkly Nation 17 June 11/6: He is, you perceive, a prattle-basket.