- headlong (adv.)
[headlong 词源字典]
- late 14c., headling, also headlings, "headfirst (downward); headlong (forward); without thinking, hastily," from hed "head" (see head (n.)) + adverbial suffix -ling. Altered by c. 1400 to conform with sidelong, etc. Its true companions are now mostly obsolete: darkling, backling, flatling, etc.[headlong etymology, headlong origin, 英语词源]