Re: Come back Soviet Union, all is forgiven.
We called the ARPANET "the internet" at least by 1970, mainly because it had become an internet ... By 1974, the word "Internet" was even ratified in the RFCs ... See Cerf & Kahn's take on the subject in RFC-675 ... and note that the research (read "bullshit sessions") that resulted in RFC-675 had started several years earlier. The name was already embedded in the collective psyche by about then.
Online ads started (in my life, anyway) when a student at Stanford sent every email account on campus a "wanna buy my bike?" email back when I was stanford!sail!vax!jake (name changed to protect the guilty; I'm archived at DejaGoo under the real name (if the alpha goo kids haven't destroyed that archive entirely)) ... Probably 1982 or thereabouts. He got yelled at, loudly, and had computer privileges revoked for the rest of the year. I'd have hung him from his thumbs in the quad if I had my way.
Footnote to history ... According to some sources (and repeated in this very august publication), HMQE2 personally sent an email addressed to "everybody on the ARPANET" on March 26, 1976. If true, this unsolicited mass emailing touting the Coral 66 compiler would be the first example of spam that we can place a name, face, product and date on. However, I doubt it's true for a number of reasons. First of all, there was no mechanism to "email all" on the ARPANET back then. Still isn't. Thankfully. Second of all, I have searched my archives, and despite having many emails from around and on that date (including roll accounts at around a dozen hosts), I see none that would correspond to the mythical "HME2" email. Gut feeling is that it was merely sent to the list of accounts on that particular machine.
So I'm happy to report that HMtheQ (RIP) was probably not an unwitting international spammer.