I live in a house over one hundred years old, replaced all the windows but one, and it is wavey.
Methinks it was wavey, the day they installed it?
Before the “float glass” process was invented, glass was rolled and was wavy. Old wavy glass is highly prized by building restorers for authenticity — I hope you keep the old glass or sold it!
Wiki - “Float glass is a sheet of glass made by floating molten glass on a bed of molten metal, typically tin, although lead and various low melting point alloys were used in the past. This method gives the sheet uniform thickness and very flat surfaces. Modern windows are made from float glass.”