The spelling of the word "Cubbage" can be explained using IPA phonetic transcription. The first syllable is pronounced as /kʌb/, similar to the word "cub." The second syllable is pronounced as /ɪdʒ/, similar to the sound of the letter "g." The double "b" in the first syllable indicates a short vowel sound, while the "a" in the second syllable indicates a long vowel sound. Therefore, "Cubbage" is spelled with a double "b" and a single "g" to accurately represent its unique pronunciation.