Trell is the Old Norse
word for slave
(as in the English word "thrall
"). A trell was usually taken while going Viking
, and was bought and sold as property. The trells lived in a separate trell-house, and could be used as soldiers, mistresses or general workforce. Trells could be killed and buried with their master on his death.
The punishments for a trell trying to escape were severe. One way of preventing this from happening again was to cut their Achilleses. That said, trells were not in general (supposedly) looked down upon as such; they were not seen as "lesser" beings in any way. Many trells became close friends with their masters, and in some sagas, trells sacrifice themselves for their master.
Much like in the Roman society, a trell could earn or buy his freedom, and did then have all rights as a citizen.