fathom
UK[ˈfaðəm]US[ˈfaðəm]
n
A unit of length equal to six feet (approximately 1.8 metres), used in measuring the depth of water.
v
To understand a difficult problem or a mysterious person after much thought.
Etymology
The word 'fathom' originates from the Old English 'fæðm', meaning the embracing arms, the bosom, or the length of the outstretched arms. This term is derived from the Proto-Germanic 'faþmaz', which carried the same sense of an embrace or an arm's length. The conceptual link is beautifully direct: the span of a person's outstretched arms became a standardized nautical measurement for depth. Over time, the physical act of embracing or encompassing something with one's arms evolved metaphorically into the mental act of encompassing or comprehending a complex idea, giving us the verb meaning 'to understand deeply'.
Analysis
The word 'fathom' is a simplex word of Old English origin. It cannot be meaningfully segmented into smaller morphemes within its modern English spelling.
Examples
The shipwreck was discovered at a depth of over a hundred fathoms.
I still cannot fathom why she made such a drastic decision.
The old sailor could fathom the sea's depth by the color of the water.