headly
Chief; principal; capital; (of sins) deadly.
archaic
O'er blows the filthy and contagious clouds / Of headly murther, spoil, and villainy.
Heady; violent; impetuous.
archaic
Where it comes from
From Middle English hedly, havedlich, from Old English hēafodlīċ (“at the top, principal, capital, deadly”), equivalent to head + -ly. Cognate with West Frisian haadlik, Dutch hoofdelijk, Middle Low German hö̂vetlī̂k, Middle High German houbetlich (archaic German hauptlich). Piecewise doublet of chefly and chiefly.
Adapted from the Wiktionary entry headly (CC BY-SA 4.0).