Definition of "collateral"

Yet the attempt may give Collateral interest to this homely tale.

1814, William Wordsworth, The Excursion

That he [Atterbury] was altogether in the wrong on the main question, and on all the collateral questions springing out of it, […] is true.

1878, Thomas Babington Macaulay, “Francis Atterbury”, in Encyclopædia Britannica, Ninth Edition‎

The pure blood all descends from five collateral lines called Al-Khamsah (the Cinque).

1885, Richard Francis Burton, The Book of the Thousand Nights and a Night, volume 5

collateral light

c. 1604–1605 (date written), William Shakespeare, “All’s Well, that Ends Well”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene i]

If by direct or by collateral hand They find us touched, we will our kingdom give […] To you in satisfaction.

c. 1603–1606, William Shakespeare, “The Tragedie of King Lear”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act IV, scene v]

"The decline in the quality of eligible collateral is a grave problem. The ECB is now buying corporate bonds that are close to junk, and the haircuts can barely deal with a one-notch credit downgrade. The reputational risk of such actions by a central bank would have been unthinkable in the past."

2016, Ambrose Evans-Pritchard, “Euro 'house of cards' to collapse, warns ECB prophet”, in The Telegraph‎

In colonial times, when land was not worth much and banks didn’t exist, most lending was based on human property. In the early 1700s, slaves were the dominant collateral in South Carolina.

2019 August 14, Matthew Desmond, “In order to understand the brutality of American capitalism, you have to start on the plantation”, in New York Times‎