To double or repeat something, or in linguistics, to pronounce a consonant sound with lengthened duration (like the 'tt' in 'butter').
From Latin geminatus 'doubled,' from geminus 'twin.' Linguists use this term to describe how many languages lengthen consonants for emphasis or grammatical reasons.
Italian speakers naturally geminate consonants—that's why 'nonna' (grandmother) sounds so different from 'nona'—the doubled 'n' is a different phoneme, not just emphasis.
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