I always wondered: “Why do they use the colon format for analogies in tests: car:steering wheel::bicycle: ? “
Now I know.
a) The : :: : format was adopted for Analogies from an EARLIER usage in mathematics: ratios / proportions.
b) I found THAT source in a text written in 1916:
“We have noticed that the notation A:B::C:D ante-
dates the year 1657. Vincent Wing, the astronomer,
published in 1651 in London the Harmonicon coeleste, in
which is found not only Oughtred’s notation A.B: :C.D
but also the modified form of it given above. The two
are used interchangeably. His later works, the Logistica
astronomica (1656), Doctrina spherica (1655), and Doctrina
theorica, published in one volume in London, all use the
symbols A:B::C:D exclusively.”
William Oughtred gets the main credit, although it is Vincent Wing, an astronomer that fixed the : :: : format.