E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The combinations called rings or corners in the commercial world. The chief merchants of an article (say sugar, salt, or flour) combine to fix the selling price of a given article and thus secure enormous profits. These enterprises are technically called trusts, because each of the merchants is on trust not to undersell the others, but to remain faithful to the terms agreed on.