The SI nano- prefix means x 10-9
The prefix "nano" = 1/1,000,000,000 indicates 10^-9 or a billionth.
'nano' = 'one billionth' = 10-9
'Nano' is not a noun; 'nano' is not even a word, it is a prefix meaning 'one billionth' or used informally as an extremely small part of a whole. Some words with the prefix nano- are nanosecond, nanotechnology, or nanoscale.
Nano- means million.