orthography – “Referer” or “referrer” – English Language & Usage Stack Exchange
First of all, I’m speaking of webpage referral. Second, let me quote Wikipedia: The misspelling referer originated in the original proposal by computer “scientist” Phillip Hallam-Baker to incorporate the field into the HTTP specification.[1] The misspelling was set in stone by the time of its incorporation into the standards document Request for Comments (RFC) 1945;…