When looking at all HTTP headers, after so many years of probably doing the same, I realized that Referrer was misspelled. This wikipedia entry has some details on why, mostly attributable to the fact that ispell (?) did not recognize either word at the time.<p>Anyway, it's a fun fact of computer history :)<p>Relevant RFC: <a href="https://tools.ietf.org/html/rfc1945#section-10.13" rel="nofollow">https://tools.ietf.org/html/rfc1945#section-10.13</a><p>Edit: added source RFC.