At LexiLine we have a page devoted to the origin of the names of the metals.
Peter van der Krogt cites to that work at his interesting site devoted to Elementymology, i.e. to the origin of the names of the elements, including metals.
We recently sent him the following observations (with some small editing corrections here) based on our reading of his work:
Thank you for including our thoughts about the etymologies of metals
in your pages. We would prefer "futuristic" to the word "peculiar" but
they are your pages, so you must use what you feel to be accurate. We
are 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.
TIN
We noticed that you have Turkish Kalay and Indo-Iranian k"alah as words 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 we 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 stie[n]am(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 – we
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-, Turkish Kalay, Indo-Iranian k"alah)
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 kassiteros 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 or like, then kassiteros would mean "like iron", "similar to 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 "to boil", as the comparable term to latvian var- als meaning "to boil".
That pretty much takes care of the etymology of words for the metal TIN.
All are related to smithing, molting and boiling.
COPPER
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.
Did some German linguist come up with that self-oriented explanation?
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". The world "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" and not really metals per se,
or as the Germans say Edelmetall.