Where does the term “two-by-four” come from and What does two by four mean?

Although two-by-threes and even two-by-twos are known and employed for certain purposes, the two-by-four is the smallest size of standard dimension lumber used today in the construction of frame buildings.

The name refers to the nominal size, in inches, of the thickness and width, respectively, of the piece, although the actual size of the standard, dressed two-by-four is, at the present time, one and five-eighths by three and five-eighths inches for a net cross-sectional area of just under six square inches rather than the eight square inches the name would imply.

The smallness of the size has led to the figurative use of the term as a derogatory appellation for anything of small or insignificant area, such as, “He lives on that little two-by-four farm on the edge of town,” or, “His shop is that two-by-four hole-in-the-wall in the middle of the block.”