sicilicus
A diacritic, resembling a 180°-rotated ‘C’ (i.e., being similar in appearance to ⟨ᵓ⟩), written atop a consonant to mark gemination, superseded in Classical Latin by doubling the letter representing the geminated consonant.
It is stated by grammarians that a sicilicus or laterally inverted Ⅽ, Ↄ, was placed above a consonant which was to be regarded as a doubled letter.
A unit of weight equal to one quarter of an uncia.
Both the pounds were therefore divided alike into 15 ores, that is, ounces; the ores into 4 skyllings, the sicilici of the Romans, and the skyllings into 4 pence by the Saxons, while the Danes used the mark of 20 skyllings, and the skylling of 2 mancuses.
Where it comes from
From the Latin sicilicus, the diminutive form of sicilis (“sickle”), so named because of its falciformity.
Adapted from the Wiktionary entry sicilicus (CC BY-SA 4.0).