Monero's naming convention of a chemical element + a star or constellation is the result of a discussion on the official forum: "Now for some fun: naming Monero releases"

Regarding alliteration:

"using alliteration / assonance for maximum awesomeness." (fluffypony)

First release with this scheme is 0.9.0 ("Hydrogen Helix") and has been chosen in thread Name the Next Monero Release!

For v0.10.0 ("Wolfram Warptangent"), the scheme has been partially ignored to honor contributor Warptangent who passed away and had done a lot of work on the project among other on RingCT.

Note: Wolfram is an other name for Tungsten. (Wikipedia, By Alchemist-hp (talk) (www.pse-mendelejew.de) - Own work, FAL, https://commons.wikimedia.org/w/index.php?curid=10424635)