[ariel]

This was discussed extensively in the past.
They are characterized by straight blade, often ( in older examples) with a broad central fuller, and characteristic crossguard: iron, cruciform, with square quillons twisted at 90 degrees .
The opinion that Kaskaras derive from crusaders' swords is, to put it mildly, untenable.
The prevailing opinion is that they derive from pre-islamic swords. Ultimately, it is likely correct, but there may be an intermediary, true, predecessor: Mamluk swords. Geographically and historically, the Sudanese must have had much more in common with Egyptian mamluks that with pre-islamic Arabs.

Here are pics from Yucel's book ( the best collection of mamluk swords, albeit of a poor photographic quality). This is a 15th century Mamluk sword with the blade and the crossguard identical to classic old Kaskara. Well before any similar Ottoman examples ( although there are no known Ottoman swords before the time of Mehmet II, so caution is needed here).
Slight difference in the form of the handle ( disk instead of pommel cap), but this is minor and may be just a labor-sparing maneuver.
Similar examples , albeit with shorter quillons of decidedly similar configuration) dating to 13-15th century, are also shown in the book, but the pics are atrocious.

Any comments?