Unfathomable
/ʌnˈfæð.əm.ə.bəl/noun
Too deep, complex, or mysterious to measure or fully understand.
Did you know?The core word fathom began as a length of outstretched arms used to measure deep water, so unfathomable originally meant something so deep it defeated measurement.
Etymological Timeline
Proto-Indo-European
PIE
*pet-
“to spread, to extend”
Old English
OE
fæþm
“an embrace; outstretched arms; a unit of measure based on arm span”
Middle English
ME
fathme / fathom
“a measure of six feet, especially for water depth”
14th Century
English
un- + fathom + -able
“not able to be measured or sounded to the bottom”
Modern English
English
unfathomable
“impossible to understand or measure fully”