The Gender of the Sun.

The PIE word for sun is something like *sawel (the transcriptions from authority to authority vary greatly). A laryngeal of some sort closes the first syllable. The word is very very old indeed; it's often compared to a remarkably similar word appearing in Semitic (is there a Uralic cognate?), and shows up in just about all the daughter languages. English sun and Greek helios are cognates.

What I find interesting is what grammatical gender it takes in the daughter languages. In Germanic, it's feminine, and  she  is personified as a goddess; compare this to Greek and  Latin-Romance where it's masculine and  he  is personified as a god. Indo-Iranian has mixed evidence; it's either neuter or masculine. In Old Church Slavonic, it's neuter; I don't know about the other Slavic languages, but suspect this is the case too. My source (EIEC at this instant) does not explicitly state the gender in Baltic, but  she is a goddess, and I would presume Balto-Slavic had it in the feminine too -- which makes for an interesting shift when we encounter Slavic. The evidence in Celtic is a little harder; the feminine-gender word survives in Old Irish as a term for 'eye'. Presumably, Hittite has it in the animate gender (does it?).

I wonder. Can we speak of an isogloss here? Balto-Slavic, Germanic and Celtic opposed to the other daughters?

My sources are less explicit about the moon, but in Germanic it's masculine as I recall. I don't remember if there is a Germanic moon-god, however.

All of this leads to some interesting comparative Indo-European mythology, but I'll reserve these thoughts for later.

Mark.