Maxperson
Morkus from Orkus
RAW says you are wrong. There is not a shared language, but all of those mystic words share the same mystical tones to make sleep. You don't get to use "Shhhh," "Somniaro," "Sleep," and "Mmm-mm-mmmm" unless they share the common mystical sleep sounds. You can change RAW with a house rule, but you cannot ignore it for this discussion about RAW.The "mystic words" include "Shhhhh", "Somniaro", "Sleep", "Mmm-mm-mmmm".
These words dont imply a shared language.
They are a kind of language, because magic can "translate" the unique idiolect of one caster into the unique idiolect of an other caster.
The Bard playing the flute or dancing silently or the Fey or the psionic manifesting innately, has nothing to do with Verbal, anyway.