Bacterial DNA is said to be naked because it is not associated with :

Bacterial DNA is referred to as 'naked' because it is not associated with histone proteins, unlike eukaryotic DNA which is wrapped around histones to form chromatin. In eukaryotes, DNA combines with histone proteins to form nucleosomes, the basic structural unit of chromatin. Prokaryotic DNA, however, is not packaged with such proteins (though it may be associated with some nucleoid-associated proteins, these are different from histones). Hence the term 'naked DNA' refers to lack of protein association.