According to this site, {}{}{}
{}
> {}
The salary white collar worker received called {}.
{}{}
> {}
The salary blue collar worker received called {}.
The sample expression from old novel,
> _ **** []{}{}_
`Third Old-Rickshaw driver we had negotiated finally approved to go to Koume with salary Otoyo afforded.`
`Sumida-River, Sumidagawa by Kafū Nagai.`
So, the salary written as {} was payed for physical work before.