1630s, "type of plasterer's cement," from French potée "polishing powder" (12c.), originally "pot-full, contents of a pot," from Old French pot "container" (see pot (n.1)). Meaning "soft mixture for sealing window panes" first recorded 1706. Figurative use in reference to one easily influenced is from 1924. Putty knife attested from 1834.
1734, from putty (n.). Related: Puttied; puttying.
A very malleable or biddable person or persons: they'll be putty and do exactly what you want (as they should) (1924+)