I'm not asking for a specific source, but how do you know this? I've just heard people saying it as 'in-SPO-ration' for so long that a -spo suffix seems more i

I'm not asking for a specific source, but how do you know this? I've just heard people saying it as 'in-SPO-ration' for so long that a -spo suffix seems more intuitively to be a truncation of -spiration.