What is the origin of the word fathom?
From an Old English word meaning "to embrace" as the measure (of water depth) came to mean a man's handspan, then two yards (six feet) when standardised.
What is the word origin for the word unfathomable?
Fathom is an Old English word that means "length of the outstretched arm" which is a measure of about six feet. As a verb fathom means to embrace, surround, envelop. As a verb fathom also has the meaning to take soundings or measure the depth of water. The figurative sense of "get to the bottom of, understand" is from around 1620s. So unfathomable - adjective means you can't get to the bottom of something or…