Etymology From Middle English *forelock, *forelok, from Old English forelocc, equivalent to fore- + lock.
1
The part of a person's hairstyle which covers the forehead.
His fair large front and eye sublime declared / Absolute rule; and hyacinthine locks / Round from his parted forelock manly hung / Clustering, but not beneath his shoulders broad:1667, John Milton, “Book IV”, in Paradise Lost. […], London: […] [Samuel Simmons], and are to be sold by Peter Parker […]; [a]nd by Robert Boulter […]; [a]nd Matthias Walker, […], →OCLC; republished as Paradise Lost in Ten Books: […], London: Basil Montagu Pickering […], 1873, →OCLC, lines 300-303:
1734, The Koran: Commonly Called the Alkoran of Mohammed, translated by George Sale, Sura 96, Congealed Blood, http://www.gutenberg.org/cache/epub/7440/pg7440-images.html Doth he not know that GOD seeth? / Assuredly. Verily, if he forbear not, we will drag him by the forelock, / the lying, sinful forelock. / And let him call his council to assistance: / we also will call the infernal guards to cast him into hell.
2 more examples
Warm with the blood of lads I know / Comes east the sighing air. / / It fanned their temples, filled their lungs, / Scattered their forelocks free;1896, A. E. Housman, A Shropshire Lad, section XXXVIII:
This little boy, still flicking his head to one side between sentences though the long blond forelock that once excused the tic had been cut […]1978, Edmund White, chapter VIII, in Nocturnes for the King of Naples, New York: St. Martin's Press, page 135:
2
The part of a horse's (or similar animal's) mane that lies on its forehead.
[…] the gates themselves slowly parted, there appeared a large horse's head, with a plaited forelock under a decorated yoke, and slowly there rolled into the road a small cart, like those driven by horse-dealers, and higglers.1898, Ivan Turgenev, translated by Constance Garnett, A Lear of the Steppes and Other Stories, New York: Macmillan, page 146:
Even Boxer was vaguely troubled. He set his ears back, shook his forelock several times, and tried hard to marshal his thoughts; but in the end he could not think of anything to say.1945, George Orwell, chapter 5, in Animal Farm:
Etymology From Middle English forelok, equivalent to fore- + lock.
1
To fix in place with a forelock (wedge)
At one extremity each pair was firmly connected by a short, massive, iron link, of about two feet in length; and, at its opposite end, a large eye-bolt was driven into each stick, where it was securely forelocked.1835, James Fenimore Cooper, chapter 14, in The Monikins:
forelock
noun
Etymology From Middle English forelok, equivalent to fore- + lock.
1
A wedge pushed through a hole at the end of a bolt to hold it in place.