I'm not so sure the match is perfect.
LAtin calamus is a loan-work of Greek kalamos, which I
suppose represents *kl.H2-mo's Arabic Q should not be PIE *k and Qalam is
lacking the expected H2. The vocalic scheme a_a is kind of odd in a noun, I
guess **qalm would be more native-sounding.
As a matter of fact, this word qalam looks like a
borrowing of kalamos.
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Ishinan's response:
You said " I'm not so sure the match is perfect. " Based
on what? Please explain what are the difference of meanings between the
Latin calamus and Classical Arabic qalam?
Beware of fictitious and unsubstantiated
reconstructions applied to the Semitic field. In addition, Indo-European
reconstructions are not always reliable and their rules do
not apply to the Semitic languages. Besides, if qalam
was a LW from the Greek or Latin, the Arabic form would have
been qlms (qalamus).
Further, there many flora glossary terms related to
pastoral cultural like grass, shoots, herb, reed, cane etc. which are
either shared or passed on from Semitic to Indo-European, not the
other way. I'll be more than happy to introduce you to them one by
one, if the discourse is civil, on topic and backed up with sources.
Ishinan