“Fathom.” It kinda means “to be able to picture mentally.” Oh, yeah. It’s also a unit of measure, but the verb has to do with thought.

If you can’t “fathom” something, it means that the very consideration of it is confusing and difficult. You can’t understand it, you can’t consider it.

It’s spelled “fathom” and it’s a measure of depth of water. A fathom is six feet. The American author Mark Twain derived his pen name from the use of a sounding line aboard a river steamboat. A sailor would stand in the bow of the ship and cast a weighted line into the water, holding one end of said line. When the ship drew up to the line and it was protruding vertically from the water, the sailor would “mark” that spot on the line where it entered the water, and then draw the line up until he saw the weight on the end. The depth of water under the boat at that point would be known by the measure of the length of the line from that point to the weighted end. The sailor would then call out the depth to the boat’s pilot in fathoms, as in “Mark: One” and “Mark: Twain.” And “Mark: Three.”…and so on. When speaking of fathoming something, you’re being asked do you understand it in depth.

It’s “fathom.” From dictionary.com:

fath·om /ˈfæðəm/ Pronunciation Key – Show Spelled Pronunciation[fath-uhm] Pronunciation Key – Show IPA Pronunciation noun, plural fath·oms, (especially collectively) fath·om, verb

–noun 1. a unit of length equal to six feet (1.8 meters): used chiefly in nautical measurements. Abbreviation: fath

–verb (used with object) 2. to measure the depth of by means of a sounding line; sound.

3. to penetrate to the truth of; comprehend; understand: to fathom someone’s motives.

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[Origin: bef. 900; ME fathme, OE fæthm span of outstretched arms; c. G Faden six-foot measure, ON fathmr; akin to patent]

—Related forms

fath·om·a·ble, adjective

fath·om·er, noun

fathom is used for measuring water depth and one fathom = 6ft

I think you mean fathom.

six feet of water depth.