Translation: The first kanji used for her surname, "to", translates to "soil, earth". The second kanji used "moe" translates to "shows signs of sprouting, budding". Then, the hiragana used to make her give name, "hotaru", translates to "firefly". So, her name would come to the translation of "Firefly Sprouting from the Earth".

In Roman mythology Saturn was a fertility deity that was associated with the soil and growing. He taught men how to till the fields and enjoyed the gifts of civilization. For Saturn, the eastern element associated with it is earth and is called the Dosei, the "Soil Star". While fireflies are often seen as symbols of dying in Japan, Hotaru's surname has to do with the idea of "growning from earth". (lots of help from Ian-san)

<< In fact, this name might even be an indirect reference to Cronus, Saturn's Greek counterpart. According to the Greek Mythology Link site, "During the reign of Cronos, they say, men did not have children, for at that time, when the universe revolved backwards, all humans came out of the earth and were therefore called AUTOCHTHONOUS." In other words, they "sprouted from the soil itself." >> (quoted from Ian-san)