Gaesum-Soliferrum

[Rumo]

Just one thing i found in my latin dictionary: soliferreum can also be found in the form solliferreum (with two L), explained with the oscan word sollus=all rather than with the latin word solus (a, um) = alone

In this case, the two elements composing the word sol(l)iferreum would be exactly the same composing the word olosideron.
May the greek word be a "translation" of the latin/italic one? The translation could have been made using in a "specialized" meaning (javeline all made of iron) a generic word already existing in greek and meaning just "all made of iron".

Also, the fact that the word sol(l)iferreum is not genuinely latine could explain why in latin it remained only with the "specialized" meaning, losing the generic one.

Thank you for your hypothesis, even though it raises more questions than answers.

It seems this etymology was provided by Sextus Pompeius Festus. However his work survived in only one manuscript, fragmentary and damaged, thus the text should be read cum grano salis.