Mnemosyne was impregnated by Zeus for nine consecutive nights, thus producing the nine muses. Among other things, she was a goddess of memory.
The number of muses increased over time from the original three. Poetic license and creeping specialization. I had been looking up Euterpe, the muse of music and of lyric poetry, called "the giver of delight." The muse of song, but got sidetracked on the general topic of the Muses.
I posted briefly on inspiration the other day, and we had "Sing, Goddess..." recently. It remains fascinating to me that our mental creations seem to come from "elsewhere," to the extent that we can imagine that they come from a supernatural source.
In my line of work, we say that such things come from the "preconscious" or the "unconscious," but that's not much different from saying they are gifts of a Muse.
Whenever a preacher says "May the words of my mouth, and the thoughts and meditations of my heart, be acceptable to You," he or she is echoing the classical plea to the Muses. Our civilization remains a Greek one.
This site tries to personalize the Muses.
Image is Dante Gabriel Rossetti's Mnemosyne (1881)