beam, girder, spar, unit or column (accounting)
桁 centers on a horizontal structural support: a beam or girder in construction, and by extension a column or place in accounting where numbers line up like beams.
桁 combines 木 (wood) with 行 (go, line), suggesting a wooden beam or horizontal line. The accounting sense likely comes from the idea of rows or columns.
A wooden 木 beam that goes 行 across, like a girder supporting a structure. In accounting, numbers are placed in columns that run across the page like beams.
For コウ, imagine a construction worker calling out 'Go!' as a wooden beam is lifted into place: 'Go!' cues コウ, and the beam goes across.
column; beam; girder; crossbeam; spar; yard
an order of magnitude higher; off by a digit; in a different league; unbelievable; incomparable; unimaginable
incredible; extraordinary; exceptional; phenomenal
bridge girder
well curb consisting of wooden beams crossed at the ends
one digit; one column; the "ones" column
three-digit number; hundreds column
last two figures of a number
main girder
two-digit number; "tens" column; two digits; double figures
five-digit number; "ten thousands" column
stringer; slanted staircase beam
complete carry
four-digit number; thousands column
number of decimal places
(sail) yard; boom
partition cap; upper plate; wall girder
(generation born in) the first nine years of the Shōwa period (1926-1934)
significant digit
overflow