Today’s book exercise includes the phrase “de mãos a abanar”. Checking what ciberdúvidas has to say in the subject, it seems there are two possible variants, one more literal than the other
Ficar/Ir COM mãos a abanar usually means your hands really physically shake (but note, not shaking hands with someone else that’s “apertar as mãos” – you squeeze hands with someone.
Vir/Ficar/Ir DE mãos a abanar means to end up empty handed. Just like in English you can come away empty handed, without being able to gain from a situation, or you can turn up empty handed, with nothing to offer in a situation. The actual example in the book uses vir as the verb, but of course it depends on the situation you’re describing – whether they are setting off with nothing, coming away empty handed or whatever. I’ve also seen a Brazilian page describing “chegar de mãos abanando” which is obviously related. They use it to describe a situation where someone arrives at a party without a present or a bottle of wine or whatever. According to the writer this is related to immigrants to Brazil in the 19th century. If they were unskilled their hands would shake due to inability to use the tools of the trade. Pardon my skepticism but this sounds like bollocks to me.