Thus, for instance, suppose that a condenser of one microfarad is being charged through a resistance of one megohm by an impressed voltage of 100 volts, the equation shows that at the end of the first second after contact, the terminal potential difference of the condenser will be only 63 volts, at the end of the second second, 86 volts, and so on.
"Hertzian Wave Wireless Telegraphy"
John Ambrose Fleming
If it has a million ohms we say it has a "megohm" of resistance.
"Letters of a Radio-Engineer to His Son"
John Mills
When you get satisfactory operation in receiving by the grid-condenser method the leak will probably be somewhere between a megohm and two megohms.
"Letters of a Radio-Engineer to His Son"
John Mills