Romance articles

I've been following this whole conversation about Romance articles, but I'm
confused about one thing.

I had always understood the articles with L to be derived from /illus/, and
that the masculine form in -o was irregularly 'el' in spanish and 'il' in
Italian because of a loss of the final -o in many environments. Vide
Italian 'lo,' which is still used in some restricted environments. So what
does this have to do with Arabic? I see how it could be argued that the
influence of Arabic made the masculine form -il/el, but it doesn't seem to
me to be necessary ...

But perhaps I'm missing the argument.

BB
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Ther cam a privee theef men clepeth Deeth,
That in this contree al the peple sleeth,
And with his spere he smoot his herte atwo,
And wente his wey withouten wordes mo.
He hath a thousand slayn this pestilence.
- Geoffrey Chaucer, The Pardoner's Tale

James E Johnson, 1920-1999