Could Brennan be the perfect name for your baby boy? The baby boy name Brennan is 7 letters long, and contains 2 vowel(s) and 5 consonant(s). Brennan is a baby boy name that starts with the letter B and ends in the letter N. The baby boy name Brennan has a popularity of 24% and is ranked 763 in the list of top 1000 most popular baby boy names. If Brennan isn't the ideal name for your baby boy then take a look here for some randomly generated names. Hopefully you'll find a more suitable first name for your baby boy than Brennan!