The Spanish word 'nácar' (meaning 'mother-of-pearl') has an interesting journey through Arabic and Catalan. It originated from the Classical Arabic root 'nqr', which meant 'to strike' or 'to hollow out'. This evolved into the Andalusi Arabic word 'naqra', meaning 'drum' or 'hollow' - likely referring to the hollow, concave shape of mother-of-pearl shells. The word then passed through Catalan as 'nacre' before finally entering Spanish as 'nácar', maintaining its meaning of 'mother-of-pearl'.

The semantic evolution from 'hollow/drum' to 'mother-of-pearl' makes sense when you consider that mother-of-pearl is found on the hollow interior of certain shells, particularly those of pearl oysters and abalones.

While 'nácar' itself is a relatively unique word in Spanish without many common derivatives, you might encounter it in compound words like 'nacarado' (pearly, pearlescent) or 'nacarino' (relating to mother-of-pearl).

English speakers might recognize this word's connection to 'nacre', which is also used in English to refer to mother-of-pearl, though it's a somewhat technical or literary term. The adjective 'nacreous', meaning 'having a pearly luster', is also derived from the same source.