Definition of "specialty"

Even men of boundless knowledge, like Humboldt, must have had once their speciality, their pet subject, or they would have, strictly speaking, no knowledge at all.

1858, Charles Kingsley, “My Winter-Garden”, in Fraser’s Magazine‎, volume 57, page 410

The specialty of rule hath been neglected:And, look, how many Grecian tents do standHollow upon this plain, so many hollow factions.

c. 1602, William Shakespeare, “The Tragedie of Troylus and Cressida”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene iii]

Let specialties be therefore drawne betweene vs,That couenants may be kept on either hand.

c. 1590–1592 (date written), William Shakespeare, “The Taming of the Shrew”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene i]

[…] in a plea to an action of debt on specialty, it is still necessary to show that the debt on which the judgment was recovered was a specialty, or to aver that the judgment was recovered before the defendant had notice of the plaintiff’s demand.

1812, Joseph Chitty, A Treatise on Pleading, with a Collection of Practical Precedents, and Notes Thereon, 2nd American edition, edited by Thomas Day, New York, Volume 2, section 456, note c