All their class held these principles: I supposed, then, they had reasons for holding them such as I could not fathom.
One never knows what she has, sir: she is so cunning: it is not in mortal discretion to fathom her craft.
St. John’s eyes, though clear enough in a literal sense, in a figurative one were difficult to fathom.
— that opened upon a careful observer, now and then, in his eye, and closed again before one could fathom the strange depth partially disclosed; that something which used to make me fear and shrink, as if I had been wandering amongst volcanic-looking hills, and had suddenly felt the ground quiver and seen it gape: that something, I, at intervals, beheld still; and with throbbing heart, but not with palsied nerves.
There are no more uses of "fathom" in the book.
Show samples from other sources
When I look at the shift my life has made in the past eight months, I can’t fathom what my life will be eight months from now.
Colleen Hoover -- Slammed
He couldn’t fathom why WICKED felt it was so important to keep their minds clean of memory.