Fog is a song by Radiohead, first heard in the year 2000 in Israel. It was released on the EP Com Lag and on the Knives Out single.

The version on Com Lag is extremely simple, but also extremely moving. It features only Thom Yorke singing over a piano, and is the version that was heard first. The song has since been expanded to include the whole band playing the tune, although I have not yet heard this version.

Of course, the meaty bits of any Radiohead song are the lyrics. The first verse talks about a "little child/running round this house" who never leaves, and to be honest I can get very little meaning out of this part. The second verse is generally the most interesting.

And what be in the second verse?

The first part says that "baby alligators in the sewers grow up fast/grow up fast". The baby alligators are unwanted, and are just flushed into the sewers-out of sight, out of mind, right?. The "grow up fast" bit does not mean growing up fast in a physical sense, more in a psychological sense; these metaphorical alligators have had to grow up fast to deal with all of the hardship and torment.

The next part says "Anything you want, it can be done/how did you go bad?". This can be taken to mean that despite the best efforts of everyone concerned, everything is going wrong and nobody can stop it at this point.

The final "real" line says "Some things will never wash away". Some torment can never be undone, and will always be there, no matter how long after the event it has been-it's the same with everything. Given the place where this was first performed (Israel) these lines taken together indicate that the song was written about the tension between Israel and Palestine, with the "baby alligators" being the Israeli/Palestinian people and the "sewers" being the disputed and violent areas. All in all, an extremely touching and moving song.

Lyrics can be found at http://www.greenplastic.com/lyrics/fog.php

I just added this on SongMeanings.net which should explain my own personal view:

It's about some horrible tragedy, some past torment in your childhood. And it'll never leave you. It'll make you grow up fast, knowing too much about the bad side of the world, and it will certainly never wash away into nothing. You can do anything you want to...but it'll never go away. A personal song, with a big personal resonance for me.