Patrick Andries wrote:
Latin numerals are not based on the position of the letter in
the alphabet, contrarily to Greek for instance.
Latin numerals are not based on the first letter of the word
they represent, with the exception of C and M, perhaps (*).
...
> (L, for instance was originally written \|/ then _|_)
...
(*) C was first written as ")|(" then was abbreviated ")" or "(".
...
The same is true for M which had, amongst its many early forms, a form close
to (I), [...]
Cf. U+2180 in <http://www.unicode.org/charts/PDF/U2150.pdf>.
Note that V is half an X (the upper half),
L emerged from half a C (the upper half of its original form),
D is half a U+2180 (the right half).
Best wishes,
Otto Stolz
