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Hekdesh is a Yiddish-Hebrew word meaning, in popular parlance, a big mess, as in, Clear up your bedroom right now; it looks like a hekdesh. (In truth, Ive heard it used colloquially only in the United States, where Yiddish was not deliberately purged from Eastern European immigrants as it was in the UK.)
Originally, hekdesh meant something very different. Money or objects pledged to the Temple were designated as hekdesh.
One could dedicate hekdesh either to the upkeep and maintenance of the Temple, or to the specific sacrifices. The owner of an object could make something hekdesh simply by saying so; even, in some circumstances just by mentally dedicating it. Once it was rendered hekdesh in this way it could not be used for any other purpose until it was formally redeemed.
At a certain point after the destruction of the Temple, the term came to refer to donations of objects to the community, particularly for use by the poor.
Hekdesh was another word for a gamach, that is a repository of often-expensive objects, such as wedding dresses, that were lent out to those unable to afford their own.
The Temple no longer stood, but this was an analogous way of contributing to the public good. Hekdeshim thus became storehouses for all of the communitys junk, and hence paved the way for the words meaning to morph into mess.