[EDIT: It seems I may have misunderstood your question. If monosyllables are, indeed, what you are looking for, please, ignore anything below that pertains to word-length. The rest should make some sense regardless.]
I don't think there's a simple answer, as there are quite a lot of factors to consider (both language-specific and [quasi-]universal). I can only offer a few loose ideas hoping that at least some of them will prove useful to you.
First of all, I'm not sure that frequency can be straightforwardly linked to euphony. Instead, I'd speculate about sonority being somehow related. Hence, I'd suggest, for instance, that the name would (1) consist of open syllables (ideally CV combinations) and the C's (consonants) be as sonorous as the particular language permits. Typically, the sounds could be approximants such as /w/ or /j/, liquids such as /l/ or /r/, and nasals such as /m/ or /n/.
On the other hand, other things should definitely be taken into account such as (2) the semantics (and connotations and allusions, e.g. how can the form be linked to whatever the services you mention represent?).
Of course, this leads to other aspects pertaining to both the form and the meaning. For example, is the word an existing one or a completely new formation, and, in the latter case, is it composed of existing morphemes, is it a blend, an acronym, an abbreviation or just an arbitrary concatenation of phonemes (e.g. based on euphony solely)?
All of the above can be seen from the poetic perspective, since aesthetics definitely belongs to important and common functions of/in language. Concepts such as alliteration, rhyme, but also rythm are just a few to think of. All these things may facilitate remembering the name.
Now, getting back to phonetics and phonology, depending on the place of their articulation, (3) you might consider avoiding repetition of the same or similar consonants in adjacent syllables to make the pronunciation as easy as possible (combinations such as /raliru/, /rirela/, /lalarile/ etc. can be notoriously tongue-twisting in some languages). On the other hand, unlike the consonants, the vowels could be all the same. And, of course, the word probably shouldn't be too long, which can also be language-specific: one, two, three, but probably not longer in languages such as English.
I suppose there are other things to consider, but the above may be a good start. Here's a random list of a few pseudo-words formed without semantic or (strictly) poetic considerations: