Lamington is a slur used to describe Australian aboriginals in a derogatory way. Most of them are dirty, as they dont bathe and therefore develop dandruff, hence the lamington look (a lamington is an Aussie cake - sponge cake with black/brown icing then rolled into dessicated coconut).
The word Lamington is a racial slur that has been used historically to degrade and dehumanize australian aboriginals. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to australian aboriginals. If you are unsure about whether or not it is appropriate to use the word Lamington, it is best to err on the side of caution and avoid using it in any situation.