The present sense is unattested in Medieval Latin or French, where the usual sense is 'a husk or pod', and by extension, 'a small unit of weight or measurement'. The present sense can be found in Classical Latin.
s.
1curr.Roman silver coin, valued at 1/24 of a solidus:
(
s.xiiiin; MS: s.xiii2/4
)
La curut dunc une munee Ki siliqua fut apelee
536
siliqua (s.xiiiin)