The spelling of "Mantini" can be explained using IPA phonetic transcription. The word is pronounced as /mæn'tiːni/. The "a" is a short "a" sound, and the "t" is pronounced with a strong dental stop. The "i" sound is a long "ee" sound, and the stress in the word falls on the second syllable. The final "ni" ending is pronounced as a short "ni" nasal sound. Overall, the spelling of "Mantini" accurately reflects its pronunciation in English.
There doesn't appear to be a widely known etymology for the word "Mantini". It is possible that "Mantini" could be a rare or obscure surname, a proper noun, or a term specific to a certain context or region. Without more information or context, it is difficult to determine the exact origins or meaning of the word.