Here are some examples:
* Irish: *airgead* (pronounced "ar-g'id")
* Scottish Gaelic: *airgiod* (pronounced "ar-g'id")
* Manx: *argid* (pronounced "ar-g'id")
* Welsh: *arian* (pronounced "ar-ee-an")
* Cornish: *arghans* (pronounced "ar-ghans")
* Breton: *arc'hant* (pronounced "ar-k'hant")
It's important to note that these are modern forms of these languages, and the words for silver may have been slightly different in ancient Celtic languages.