This might be the historical meaning of the word but it's certainly not the meaning of the word today and I'm doubting it was the meaning of the world at the time of the author.

Take this as an example: https://en.wikipedia.org/wiki/Robotnik_(1894%E2%80%931939) This newspaper was first published around the time of the authors life. It has no connection to the slavery just to the labour and labourers.