One of the earliest known Celtic people in Britain was
Cassi:
https://en.wikipedia.org/wiki/Cassi, their leader was
Cassivellaunus:
https://en.wikipedia.org/wiki/Cassivellaunus
The
Common Brittonic personal name
Cassiuellaunos stems from the word
uellaunos ('chief, commandant').
[1] The meaning of the prefix
cassi- has been debated, but it possibly signifies 'tin, bronze'. Cassivellaunus may thus been translated as 'Chief-of-Tin', that is to say 'the inflexible'. The personal name
Ver-cassivellaunus ('True-Chief-of-Tin') is related.
[2]
And you read here about
Cassiterides:
https://en.wikipedia.org/wiki/Greeks_in_the_United_Kingdom#Cassiterides
Cassiterides
Ancient Greek writers, including
Herodotus, mention a group of islands which were called
Cassiterides. Modern researchers suggest that they may refer to the
British Isles.
The
Cassiterides (
Greek: Κασσιτερίδες, meaning "Tin Islands", from κασσίτερος,
kassíteros "
tin"):
https://en.wikipedia.org/wiki/Cassiterides
And about kassíteros:
https://en.wiktionary.org/wiki/κασσίτερος
An
Elamite origin has been suggested but, according to Beekes, the group "σσ/ττ" is typically
Pre-Greek, so the word would have come from Greece or Western Anatolia, like
μόλυβδος (mólubdos, “lead”), but even if so, the word might still go back to Mesopotamia, representing the name of the
Kassites, who settled near
Elam and major sources of tin. Compare also the etymology of
Arabic مَرْقَشِيتَا (marqašītā, “
marcasite”). Related to
Sanskrit कस्तीर (kastīra, “tin”).
About
Kassites:
https://en.wikipedia.org/wiki/Kassites
Glass works
Remnants of two Kassite glass beakers were found during the 1964 excavation in a (c. 800 BC) destruction layer of
Hasanlu, in northwest
Iran. The mosaic glass beakers are thought to have been heirlooms, possibly for ritual use the find spot being a temple. The panes of glass used to create these images were very brightly colored, and closer analysis has revealed that they were bright green, blue, white, and red-orange.
[54] A Kassite text found at
Dur-Kurigalzu mentions glass given to artisans for palace decoration and similar glass was found there.
[55] Other similar glass dated 1500 BC was found at
Tell al-Rimah.
[56]