The correct spelling of "doth top of head" is actually "off the top of my head." This phrase is often used to indicate that an answer or response is being given without much thought or preparation. The IPA phonetic transcription for "off" is /ɒf/ and for "the" is /ðə/. "Top" is spelled as it sounds /tɒp/, and "my" is transcribed as /maɪ/. "Head" is pronounced /hɛd/. Therefore, the correct spelling reflects the pronunciation of the phrase.