A「person's head and neck, in danger」or「head rolled person」is some sort of a BEHEADING, DECAPITATION—but not only the head upon one's shoulders—elements for「person」are「taut, leashed, or bound erection」and both a person giving head and a person getting head have「head and neck in danger」the former from asphyxiation and the latter from gnashing teeth or some other means of mutilation. Describing a human being without a head on his shoulders as DEFICIENT, BROKEN and MISSING SOME PIECES, BECOME SHORTENED, CHIPPED, NEGLIGENT and so on is a bit weird, since in most cases such a condition will cause fairly rapid death. Instead, as is made obvious by the use of this glyph as an element, likely referred to the nether head being DECAPITATED by a vengeful service provider or wife who「bobbitted the schmuck」for various reasons, or a head breaking into fragments due to disease as a matter of course, but with the subject remaining alive and actually walking around for a while longer. May be the source of the English term「heck」as a merging of 'head and neck' and a reference to being in hell, missing one's head in the nether region.
　「Head rolled person」may be YAWNING, a GAPING, wide-open mouth (for various reasons), or decapitated torso BLOWING HARD (for various reasons, and various fluids). A person will often roll back their head, facing straight up while YAWNING, also common among penguins, dogs, primates and most animals (all the vertebrates) that yawn. With one's severed nether head「head rolling」around on the ground (see other glyphs that use this as an element for further details) folks might stare with mouths wide open, and gasp. Some empirical data supports that contagious yawning is a measure of empathy. Perhaps related to open-mouthed BLOWING HARD (for various reasons) or seeing someone walking around headless, whether deserved or undeserved. While the external dictionaries emphasis 欠 as 'the yawning radical,' it cannot be said that oscitation is anywhere close to the main meaning…rather, look for a deficiency, missing parts, something broken, fragmented, splintered, and shortened. Researchers tell us that yawning serves to cool the brain in order to maintain optimal working temperature for continued thinking and alertness.

Modern definitions (that generally disregard history) …excluding politically incorrect concepts and other meanings deemed offensive today; may list only pigeonholed definitions, euphemisms, or meaningless mnemonics)
Chinese: deficient; to owe; to lack; yawn
Japanese: yawn, yawning, kanji "yawning" radical, lack, deficiency, vacancy, to chip, to nick, to break, to crack, to lack, fragment, splinter, wane, to miss, to fail, broken pieces, to be chipped, to be damaged, to be broken, to be lacking, to be missing, to be insufficient, to be short, to be deficient, to be negligent toward, to wane, to go into eclipse
Unihan extended: owe, lack, be deficient
EDRDG: lack; gap; fail; yawning radical (no. 76)