Green’s Dictionary of Slang

a confidence trickster, esp. one posing as a ‘gentleman fallen on hard times’.

1698		N. Ward London Spy I 7: To be short with you, he is one of the Gentile Mumpers we call Cadators; he goes a Circuit round England once a Year, and under pretence of a Decay’d Gentleman, gets both Money and Entertainment at every good House he comes to.
1741		Canting Academy, or the Pedlar’s-French Dict. 118: A common Beggar Cadater.
1760		T. Brown Works (1760) II 179: You... sot away your time in Mongo’s fumitory, among a parcel of old smoak-dry cadators [F&H].
c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Cadators Beggars who make Circuits round the Kingdom, assuming the Character of decayed Gentlemen.