The verb requite simply means to "repay", from the Middle English requite or requight. The OED has examples from 1440, twentieth-century ones being the following:
1919 Outing Mar. 314/1 How Jackson requited their aid will be seen
in the sequel.
1938 E. Waugh Scoop 56 ‘It was the act of..a fellow Englishman,’
said the little man simply. ‘I hope that one day I shall have the
opportunity of requiting it.’
1987 Nature 16 July 188/1 The decision of the British Midland
Bank..to set aside an extra £915 million in respect of overseas loans
unlikely to be requited.
The OED attributes two senses to unrequited, the first monetary and the second that which concerns human feelings e.g. unrequited love. Recent examples of the former are:
1915 T. G. Soares Social Inst. & Ideals Bible iv. 49 The bitter
unrequited toil which the great kings and nobles exacted from their
hordes of captives.
1947 Manch. Guardian 16 Apr. 6/7 These great balances can never be
discharged or even diminished except by unrequited exports unbalanced
by imports.
2004 P. R. Kumaraswamy in E. Karsh Israel 255 The prolonged
Israeli overtures remained unrequited.
However there is no doubt that the more frequent use of the term nowadays concerns the matter of human feelings and as well as "love not repaid", it can also apply but less commonly to unrepaid hatred. The full entry for sense 2 is:
- Of a feeling, esp. love or desire: not reciprocated, not returned. In later use also applied to love, desire, etc., which is thwarted or remains unfulfilled for reasons other than lack of reciprocation.
1557 Earl of Surrey et al. Songes & Sonettes sig. G.ii (heading)
Complaint for true loue vnrequited.
1645 D. North Forest of Varieties i. 40 He that loves with
unrequited love, And finds his heat ingender no reflection.
1694 N. H. Ladies Dict. 333/2 Thus begins his [sc. Ovid's] Remedy
for such unrequited Love.
1767 T. Hull Perplexities iv. 59 No hope of perfect, or of lasting
rest, While unrequited love corrodes the breast.
1814 Wordsworth Excursion vi. 254 He was crazed in brain By
unrequited love.
1865 C. M. Yonge Clever Woman I. 298 Sisterly affection cannot
blind me to the fact of that unrequited admiration for your honourable
rival.
1913 J. J. Underwood Alaska 373 His [sc. Rezanof's] bright mind
and courtly manners won..the heart of..Dona Concepcione. The story of
their unrequited love was later woven into a lyrical romance by Bret
Harte.
1916 B. Russell Justice in War-time 54 The Germans, we are given
to understand, hate us with a bitter hatred, and long to believe that
we feel towards them as they feel towards us; for unrequited hatred is
as bitter as unrequited love.
1931 Times of India 28 Apr. 8/4 The ruthless murder of a child
wife had been committed as a result of unrequited lust and unsatisfied
desire.
1993 Times of India 21 Feb. 15/5 The song..comes at a point when
the couple's love is about to go unrequited.
2009 J. Holmes Darwin's Bards vii. 200 The Renaissance sonneteers
wrote about unrequited desire from the male lover's perspective.
– user 66974 Jul 19 '18 at 13:16What's so idiomatic about the term "unrequited" to be so closely and exclusively associated with "love"? Was it, perhaps, often used by writers and poets in the past to talk about love pains to make it a set phrase?
Or is the connection via the original "money concept" in the sense that it originally referred to "paid" love?
The evolution or etymology of "unrequited"doesn't make it "idiosyncratic", does it?
– Robbie Goodwin Jul 19 '18 at 20:48