Etymology From Middle English thorn, þorn, from Old English þorn, from Proto-West Germanic *þorn, from Proto-Germanic *þurnaz, from Proto-Indo-European *tr̥nós, from *(s)ter- (“stiff”). Cognates Near cognates include West Frisian toarn, Low German Doorn, Dutch doorn, German Dorn, Danish and Norwegian torn, Swedish torn, törne, Gothic 𐌸𐌰𐌿𐍂𐌽𐌿𐍃 (þaurnus). Further cognates include Old Church Slavonic трънъ (trŭnŭ, “thorn”), Russian тёрн (tjorn), Polish cierń, Kamkata-viri taňi, tai (“thorn”), Sanskrit तृण (tṛ́ṇa, “grass”).
1
Biology, Botany, Natural sciences A modified branch that is hard and sharp like a spike.
2
Any thorn-like structure on plants, such as the spine and the prickle.
On the mountains a few junipers and piñons are found, and cactuses, agave, and yuccas, low, fleshy plants with bayonets and thorns.1895, J[ohn] W[esley] Powell, chapter I, in Canyons of the Colorado, Meadville, PA: Flood & Vincent; republished as The Exploration of the Colorado River and Its Canyons, New York: Dover, 1961, →ISBN, →OCLC, page 22:
3
Any shrub or small tree that bears thorns, especially a hawthorn.
the white thorn
the cockspur thorn
4
Figuratively That which pricks or annoys; anything troublesome.
There was given to me a thorn in the flesh, the messenger of Satan to buffet me.1611, The Holy Bible, […] (King James Version), London: […] Robert Barker, […], →OCLC, 2 Corinthians 12:7:
The guilt of empire, all its thorns and cares, / Be only mine.1692–1717, Robert South, Twelve Sermons Preached upon Several Occasions, volume (please specify |volume=I to VI), London:
5
A letter of Latin script (capital: Þ, small: þ), borrowed from the futhark; today used only in Icelandic to represent the voiceless dental fricative, but originally used in several early Germanic scripts, including Old English where it represented the dental fricatives that are today written th (Old English did not have phonemic voicing distinctions for fricatives).
In Old English manuscripts thorn and eth did not have different phonetic values but were used positionally[.]1985, Robert Burchfield, The English Language, Oxford: Oxford University Press, page 175:
Etymology From Middle English thorn, þorn, from Old English þorn, from Proto-West Germanic *þorn, from Proto-Germanic *þurnaz, from Proto-Indo-European *tr̥nós, from *(s)ter- (“stiff”). Cognates Near cognates include West Frisian toarn, Low German Doorn, Dutch doorn, German Dorn, Danish and Norwegian torn, Swedish torn, törne, Gothic 𐌸𐌰𐌿𐍂𐌽𐌿𐍃 (þaurnus). Further cognates include Old Church Slavonic трънъ (trŭnŭ, “thorn”), Russian тёрн (tjorn), Polish cierń, Kamkata-viri taňi, tai (“thorn”), Sanskrit तृण (tṛ́ṇa, “grass”).
1
To pierce with, or as if with, a thorn (sharp pointed object).
[…] human nature is, above all things, lazy, and needs to be thorned and goaded up those heights where it ought to fly.1869, Harriet Beecher Stowe, Old Town Folks:
Even Judge Bradley's callused sentiments were thorned by the narration of Jaclyn's journals.2003, Scott D. Zachary, Scorn This, page 175: