Meaning
To go overboard / To go off the deep end
Example
Na festa de ontem, ele enfiou o pé na jaca e bebeu demais.
At yesterday's party, he went overboard and drank too much.
Origin
Despite the modern wording, enfiar o pé na jaca ("to stick one's foot in the jackfruit") was originally enfiar o pé no jacá. A jacá (from Tupi) was a basket of bamboo or vine slung on the flanks of pack animals. Drovers would stop at roadside taverns and, once drunk, miss their footing when remounting and plant a foot right in the jacá.
Source: Qual é a Gíria?.
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More idioms
Acertar na moscaTo guess correctly / To hit the nail on the headAmigo da onçaA fake/false friendAndar na linhaTo toe the line / To behave properlyArmar um barracoTo cause a public sceneRodar a baianaTo cause a public scene / To go ballisticArrumar sarna pra se coçarTo ask for troubleArrastar as asasTo hit on someone / To flirtAbrir o jogoTo come clean / To open upArregaçar as mangasTo roll up one's sleeves / To get to workAgarrar com unhas e dentesTo hold on for dear life / To seize an opportunity