Green’s Dictionary of Slang

(US drugs) a narcotics addict.

1926		Times Dispatch (Richmond, VA) 17 Oct. 7/7: Hygelo — Drug user.
1935		A.J. Pollock Und. Speaks n.p.: Hygelo, a morphine fiend; a hophead.
1949		Monteleone Criminal Sl. (rev. edn).
1953		Anslinger & Tompkins Traffic In Narcotics 310: hygelo. A drug addict.