Obviously the coroner between the sheets like the Isleys
The title track of this Isley Brothers album was sampled for The Notorious B.I.G.’s “Big Poppa.” Dead bodies are often covered in sheets. Kendrick is hinting that the coroners (doctors working in morgues to determine the cause and time of death of the deceased) have been kept busy, going sheet to sheet.
Many coroners actually have no credentials, and are hired to cover up many murders, usually at the hands of policemen, to keep them from being charged. Hence them being between the sheets.
Kendrick also slurs “Obvi-” at the start of the bar to make it sound like IV, thus continuing from the rhyme scheme of the previous bar.
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