what is AiO Firmware Updater

Several printer companies use the AiO name to signify an All-in-One printer that is capable of Fax,Scan,and Print. It is possible the printer has a firmware update as that is the way the printer software gets updated.

Can you please provide some context?

The only Mac reference to "AIO" is an long-obsolete PowerMac, this beast:

[image from the MacTracker database]

That is the PowerMac G3 All-in-One, or "AIO." Some people informally call iMacs and eMacs "all-in one" as well.

The other web references I'm finding seem to refer developer tools so that why some context may help us better help you.