The "six" in the expression comes from the six feet that make up a fathom which is a little less than two meters.

VOA: special.2009.05.24

The "six" in the expression comes from the six feet that make up a fathom -- which is a little less than two meters.

VOA: special.2011.03.06

They place their hands and feet in the cracks and then work their way up.

VOA: special.2009.01.07

Down two and a half. Kicking up some dust. Thirty feet.

VOA: special.2009.07.15

thirty-six feet per second up. Very smooth, very quiet ride."

VOA: special.2009.07.15