The reason why Huck still uses the term "nigger" even when refferring
to his friend Jim, is because yes, at the time it was a commonly used
word, but also I think it would have been socially unacceptable not to
refer to black people as niggers at the time. Huck was slightly weary
about what people would think of him for running around helping a
black man escape in the first place, but then to have respect for the
man as well, I think was just pushing the limit too much for Huck. As
much as he wanted to help Jim, he seemed to have kept thoughts of what
people back home would think of what he was doing, in the back of his
mind throughout the course of his journey with Jim. The section that
was alluded to last class about how Huck thought to himself how he
couldn't help but feel bad for helping Jim escape is a perfect example
of this. It was almost as if Huck felt like he was betraying his
people back home by helping not just any black man, but one of their
own slaves, to escape. Another reason Huck may have continued using
the word nigger is so that it wouldn't seem as suspicious that they
were traveling together. Calling Jim "nigger" even to his face,
probably made it more believable that Jim really was a slave of Huck's
family, and not a friend of his. Another observation is that Twain
could be having Huck continue to refer to Jim as a nigger so that the
few times he does refer to Jim as a man and not a nigger, it seems
very meaningful. For example, after Jim is treated by the doctor, Huck
says that he was glad the doctor saw that Jim was a good man, just as
he did himself. I think that Twain saves opportunities like this one,
where it shows almost a turning point in people's attitudes, by
continuing to have Jim be referred to as a nigger except in certain
parts.