What do you mean by hand span, cubit fathom ?

The cubit is the measure from your elbow to the tip of your middle finger when your arm is extended.

The hand-span is the measure from the tip of your little finger to the tip of your thumb when your hand is stretched out.

Fathom

Fathom is the unit of length used principally in the measurement and specification of marine depths.

A fathom  (ftm) = 6 feet or 1.8288 metres