Green’s Dictionary of Slang

an empty talker, a chatterer, a liar; thus bonse, to talk idly, to lie.

1655

Mercurius Fumigosus 51 16-23 May 5: Some of these new Children of Light intend to convert Grubstreet, concerning the Art of Lying, which the Grubs, Bonsers and Poeticall Rapture [?] makers do by the help of Pluto challenge all their dear Brethren, the inlightened Quakers, Ranters and Shakers, or any of the Spiritual Gypsies, by what names or Titles soever distinguished at the Art of Bonsing, Lying, faining, dissembling [etc].