The term 'BABY's Piggie' is a reference to the nursery rhyme 'This Little Piggy'. The crossword solution for this term is TOE, which is a three-letter word. This is because the nursery rhyme includes the line 'This little piggy went to market, this little piggy stayed home, this little piggy had roast beef, this little piggy had none, and this little piggy went wee wee wee all the way home'. The last line of the rhyme refers to the BABY's TOE, which is why the crossword solution for 'BABY's Piggie' is TOE.