Does the Greek word kannabis which is hemp derive from the Hebrew "sweet cane" in Ex 30:23? And if so: Did they smoke it?
First since there is a Greek word for hemp, that is kannabis, (the Latin word for hemp is cannabis.) it would seem clear that if the Greek word were derived from the Hebrew words "q'neh-bosem" or that the Greek writers of the Septuagint would have known that derivation and have written kannabis meaning cannabis or hemp in Ex 30:23 instead of (kalamos) which means reed or cane, which is the same Greek word used for papyrus and all other reeds. The coincidence of similar sound between q'neh-bosem and cannabis is probably just that, coincidence.
In Ex 30:23
the mixture of spices which were to be mixed together which has among them the Hebrew words that your Rabbi says refers to cannabis could hardly be an intoxicating potion no matter what the composition of the "chrism"since it was to be used for pouring as an anointing oil on the head of Aaron and his sons and the conclusions of all the mixing is: "This shall be an holy anointing oil unto me throughout your generations." So it really doesn't matter if you defend the herbs or not that were in this oil. What ever the mixture was made of, the result was not to send Aaron on a "high." Even if hemp, though doubtful, were in this passage, it would not be justification of its use as a hallucinogen.
But the derivation of the word that has been given to you seems to me to be in error. The Hebrew word for Calamus in Ex 30:23 is made up of two words. They are qeneh-bosem. The word bosem is "sweet: (just above this is qiniman-bosem which is translated "sweet cinnamon") Again bosem is "sweet". That leaves us with the word qeneh (actually q'neh) which is only related to hemp in that hemp is also a reed or a cane. But is hemp a "sweet" cane? I don't know as I have never even seen a part of the plant. I suppose however that hemp is not a "sweet" cane. I have smelled the aroma at hippie gatherings at Stone Henge and I did not consider it sweet. Thus what ever was in the mixture of anointing oil, called calamus in English, it was probably not cannabis or hemp
The word calamus is used 3 times in the KJV. Of these both the Song 4:15 and the Ezek passage have the word q'neh in Hebrew without the word sweet following as in Ex. There is no "bosem" Thus Calamus is a proper translation of q'neh both of which mean reed or cane and they are generic, that is any reed or cane. Again, the word calamus in Song 4:15 is from the Hebrew q'neh alone. The word bosem (sweet) is not in the text in Song 4:15. The word q'neh translated calamus here appears 62 time in the OT and is translated reed, cane, spear, pen etc. beside calamus.
Now let us do the word cannabis. There is no word for this drug in Biblical Hebrew just as there is no word for galaxy in Biblical Hebrew since Galaxies were not discovered until the early part of the 20th century. Yes there is a word for galaxy in modern Hebrew,- it is a transliteration "galaqsah" an obvious transliteration of an English word, and so the word for cannabis in modern Hebrew is "qannabbos" which is obviously a transliteration of the English or Greek word. Thus the Hebrew word for hemp is derived from English (or Greek) not ancient Levitical Hebrew in Ex 30:23. Cannabis then is not mentioned in Ex 30:23 but "sweet cane" is mentioned
The word "calamus" as you have already discovered is derived from Greek. The Greek word (Kalamos) is used in the LXX in place of q'neh in Ex 30:23 and simply means reed or cane, and as the measuring reed used by Ezekiel to measure the temple of his vision. It stands for any kind of reed or cane. There may be a remote possible phonetic relation between hemp which is a reed called cannabis and the Greek word for reed which in English is calamus but there is not any Hebrew connection. And in spite of what I just wrote, it is very doubtful there is any etymological relation between the words cannabis and calamus.
Thus I would say your Rabbi smokes weed and would like to find some Biblical justification for it, rather than to say he is an expert in ancient Hebrew herbal mixtures. I doubt very much that he is.
I agree that legal opposition to the use of this weed and the penalties for possessing it is over done by authorities in our government at this time, but I do not use it , never have, and believe no Christian would use it except a backslider or one just baptized trying to get over it. Get high on the Holy Ghost just as it says in Eph 5:18 don't get high on booze, but fill yourself with the Holy Spirit". (Miller's translation) means "don't get high on weed, but let the Holy Spirit be your high through Christian music, worship, etc.
Let us be sure to see that even if there were a connection between the hemp plant and Ex 30:23 it was not going to be used for a hallucinogen. That kind of worship is a part of idolatrous and forbidden speaking-to-the-dead religions but not a part of Mosaic or Christian worship. Hemp makes good rope and good sack cloth. I am sorry that the misuse of the plant creates a shortage in the good uses the plant can be put to.