The correct spelling of the word "twilley" is actually "twill". The reason for this misspelling may be due to the fact that the final consonant sound in the word is often pronounced as an "ee" sound, rather than a true "l" sound. The IPA phonetic transcription for "twill" is /twɪl/, with the first sound being a voiceless bilabial stop (t), followed by a voiced alveolar approximant (w), and ending with a voiced alveolar lateral approximant (l).