"Secret Service name". For Clinton it is "Evergreen" and for Trump it is "Mogul".
- Who gives these names?
- For me the phrase "Evergreen" has more positive sense than "Mogul". But I don't know if it comes true for US culture?
It's a Secret Service code name.
They are assigned by the White House Communications Agency.
According to an article by the Chicago Tribune:
These not-so-secret names are chosen by officials at the White House Communications Agency, which was not inclined to comment on the selection process. In a previous news report, an agency spokesman said the names are assigned by "sheer whim."
While the process is not public, there are anecdotal reports that the protected person has input on their secret service codename.
For example: Karenna Gore, daughter of vice president Al Gore, wrote in 1997:
Ever since four years ago, when I was put on the spot and told "two syllables" and "It has to start with an s", I have been cringing in the back seat when identified as "Smurfette".
Generally, the primary protectee (i.e. POTUS, VPOTUS, a presidential candidate) is given a name that is reflective of them and their past history or in jokes (i.e. Reagan as Rawhide was due to his career as a Cowboy actor. Ben Carson was given Eli, probably due to him being one of the more openly religious candidates during his bid for presidency.). The Primary's family are given names that start with the same letter as the Primary's code name. Hillary's name comes from her days as FLOTUS, where Bill was Eagle. Since she's been under Secret Service protection since Bill was campaigning in 1992, there was never a need to change.
The names themselves are generally picked because they are easy to pronounce and not likely to be used in everyday chatter (The Secret Service is probably not going to be referring to the refraction of light following a rain storm, but their protectee "Rainbow (Nancy Reagan)" on radio chatter. The two syllables mentioned above don't seem relevant as Donald Trump Jr. is Mountaineer... multiple syllable words are harder to confuse and can be figured out if a particular radio has interference.
Don't know how it's currently done, but during JFK it was split into groups, and everyone in a group had code-names starting with the same letter. The code-name and letter for a group, would occasionally change. Would imagine a similar system though...
In William Manchester's book "The Death of a President" (about the JFK assassination) it's mentioned that during the JFK presidency, the following codes were used (during travel/trips). These were the current codes before the trip to Dallas (I'm transcribing from an audio-book and English isn't my first language):
The Ls - President and his family:
The Ds - Secret Service:
The Ws - Staff:
The Vs - The Vice-President and his family:
It's also mentioned that code and grouping occasionally changed, so one particular person went from being PORTER (P), to SUPER (S), to RIVER (R).
I would be surprised if any single agency of US govt would be permitted to create names for any person program or system since there would be a danger of duplication and possible confusion and damage to govt assets or personnel. In UK it appears the e.g. code names are taken in sequence from a centrally administered list that is common to GCHQ, MOD, MI5, MI6 and perhaps other parts of Gov.t.