Probably calque of English piece of shit (borrowed at the end of the 20th century after the dissolution of the Soviet Union, with the rising influence of American popular culture in Russia), to denote the same idea that ку́ча (kúča) is traditionally used for, but usually only literally (never of a thing or person).
The calque nature of the idiom is obvious to a native speaker since кусо́к (kusók, “piece”) presupposes це́лое (céloje, “the whole”) in Russian. For example, кусо́к пирога (kusók piroga, “a piece of a pie”). While the English idiom piece is used in the sense of an item belonging to the class of similar items, the meaning of Russian кусо́к (kusók) is closer to that of the English word part.
Since the source of the calque is transparent, the synonymous combination кусо́к говна (kusók govna) is possible as well, but the usage of both phrases is restricted even in colloquial speech.
кусо́к дерьма́ • (kusók derʹmá) m inan (genitive куска́ дерьма́, nominative plural куски́ дерьма́, genitive plural куско́в дерьма́)
| singular | plural | |
|---|---|---|
| nominative | кусо́к дерьма́ kusók derʹmá |
куски́ дерьма́ kuskí derʹmá |
| genitive | куска́ дерьма́ kuská derʹmá |
куско́в дерьма́ kuskóv derʹmá |
| dative | куску́ дерьма́ kuskú derʹmá |
куска́м дерьма́ kuskám derʹmá |
| accusative | кусо́к дерьма́ kusók derʹmá |
куски́ дерьма́ kuskí derʹmá |
| instrumental | куско́м дерьма́ kuskóm derʹmá |
куска́ми дерьма́ kuskámi derʹmá |
| prepositional | куске́ дерьма́ kuské derʹmá |
куска́х дерьма́ kuskáx derʹmá |