hypothecate

To pledge (something) as surety for a loan; to pawn, mortgage.

‘My husband, Jasper Murdock, provided in his will that no part of his collection might be sold, loaned or hypothecated during my lifetime.’

To designate a new tax or tax increase for a specific expenditure.

The levy needed primary legislation and permission from the Treasury to hypothecate the proceeds back into the new line. It meant that the Greater London Authority could borrow against future income from the levy.

To designate in advance the specific purpose of expenditure for government revenues (especially taxes).

"Levying customs duties and excises on necessities also ensured a relatively secure source of revenue. Revenues were generally hypothecated in an attempt to draw support from the public, for example funding an orphanage, gaol, hospital equipment and building works around Sydney." A brief history of Australia's tax system; Sam Reinhardt and Lee Steel; 04 September 2006