Peter van der Krogt cites to may work at his interesting site devoted to Elementymology
i.e. to the origin of the names of the elements, including metals.
I recently sent him the following observations based on my reading of his work:
"Thank you for including my thoughts about the etymologies of metals in your pages. I would prefer „futuristic" to the word „peculiar" but they are your pages, so you must use what you feel to be accurate. I am not sure, however, if departing from mainstream thought is properly categorized as „peculiar", especially in linguistics. Most mainstream linguists are still living in the 18th century and have not caught up with the times. The Baltic languages are very archaic (are the oldest still spoken Indo-European tongues) but since most linguists do not speak them and are too lazy to learn them, they ignore them, to the detriment of etymology.
I noticed that you have Turkish Kalay and Indo-Iranian k"alah for tin. The Latvian term for „smith" is Kalej(s) so that we surely have an ancient connection there.
Latvian also makes sense of Latin stannum since Latvian stien(is) means „bar" or „ingot" which I see as related to Latvian stiep-, a word applied to things that are ductile, extensible, tensile, i.e. capable of being stretched out. Latvian stiepam(s) or stienam(s) would mean literally „stretchable". In other words, the Latvian term for „bar" or „ingot" is probably based on the molten „shapeable" form of bars or ingots as ancient smiths formed them before they hardened during the process of cooling.
Note that you can thus isolate three separate lines of etymology for words naming tin:
1) one line of etymology based on naming the metal by the ductile bars and ingots in molten form (Latvian stien-, Latin stannum – I place Latvian first because it is simply more archaic than Latin)
2) one line of etymology based on the firing procedure in the oven (Latvian alva, Slavic olovo), i.e. adding more air to the fire for greater heat
3) one line of etymology based on „smithing" per se (Latvian kalej-)
The Hebrew term b-dil may be related to Latvian dzel(s) „iron" (see dzel- at http://www.lexiline.com/lexiline/lexi139.htm. That makes sense since the Greek comparable term kassitoros and Arabic qaSdir are surely to be divided as a word into the enclitic particle ka- plus sidero-, the Greek term for „iron". Since
Latvian ka- means „as", kassiteros would mean „like iron". Hence, the hypothetical *ka-tsvi?ra- looks pretty good from here. The root of sidero- is surely found retained in e.g. German sieden meaning „boil", the comparable term to latvian vār-. „boil".
That pretty much takes care of the etymology of words for Tin. All are related to smithing, molting and boiling.
You explain northern Slavic Miedz or MED for Copper as being corruptions from the German Schmied meaning „smith". This is rather doubtful as the etymology for German Schmied viz. English Smith is not even known beyond Old Norse smidhja.
I bet some German linguist came up with that one.
In Latvian MAT(et) means „to tarnish" as copper does or to „deaden" or „dull" metal, so that here you have a case of copper being named for that feature.
You probably also see Latvian MAT- in the root of the English word METal, i.e. as named for those metals which „tarnish". Metal is currently seen to stem from Greek metallon, and that word too is surely rooted in MET- or MAT- „tarnish", which appplies to almost all metals except those such as gold which we view to be „noble metals", or as the Germans say „Edelmetall".