When you say that someone makes no bones about something, what you mean is that the person is very frank about it; he speaks plainly, and does not attempt to hide the truth. For example, if a person makes no bones about a scandal in his past, he talks about it candidly — at times, leaving the listener embarrassed!
Examples: The teachers made no bones about their dissatisfaction with the contents of the article. * Radha made no bones about her dislike for crossword puzzles.
Some scholars believe that the idiom comes from games played with `dice’. During the early 14th century, dice were made from bones; therefore, it comes as no surprise that the slang term for these small cubes was `bones’. I understand that even today, it is common practice among gamblers to talk to their dice and blow kisses on them before throwing them on the table. When a person makes `no bones about it’, he rolls the dice without really doing any of these things. In other words, he doesn’t plead with the dice to give him a particular number. This is just one of the explanations for the origin of the idiom.