From what I can remember, *nix has always used login. When Novell came around, they continued usage of the term login. Anytime someone mentions login scripts, I immediately think of NetWare.

The first time I ever remember hearing the term logon it was for Windows NT 3.5. I guess MS just couldn't live with the standard terms and had to start making up their own. The only other possibility is that OpenVMS may have used that term and NT kept it (along with the kernel).

I'm pretty sure that logon is an MS invention since people that don't dabble in Windows at all, all say login.
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Stevie