The spelling of "drennan" can be explained using IPA phonetic transcription. The first syllable is pronounced as "drɛn," with the "e" sounding like the "e" in "bed." The second syllable is pronounced as "ən," with the neutral vowel sound known as a schwa. The final syllable is also pronounced with a schwa, making it "ən" as well. The spelling of "drennan" reflects the sound of the word and the placement of stress on the first syllable.