A New Dictionary

Ameliorate - (cause to) become better.

Amelioration, in regards to lexigraphy, is the process by which a word aquires a more favourable sense or tone than its original one.

The word 'nice' entered Middle English in the sense of 'stupid or foolish'. 'Nice' is derived from the latin word 'nescius', which means 'ignorant' (literally 'not to know').
From the idea of foolishness or ignorance derived the sense of 'modest, shy', which developed into a range of further senses - 'cautious, fastidious, discerning, refined, subtle, delicate'.
Finally, the common modern semse emerged - 'pleasant, enjoyable'

So remember this next time someone calls you nice, they are unintentionally calling you ignorant!!

Adapted from 'nice and luxurious' in What's in a Word by John Kahn