https://en.wikipedia.org/wiki/R.U.R. That's the play that introduced it and it's looking like the word means "forced labour" rather than just "work". Which you could say is slavery.
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.