Contact Naming

My girlfriend who is 47 had an old boyfriend that she said liked to have sex for two (2) hours. She is from China, very well educated (Masters/Graduate level) and English is her third language. She speaks broken English and is still learning. She has this old boyfriend listed in her phone contacts as DAX. I didn't understand why she listed him as DAX and was curious as to whether this word had a special meaning. When I looked up the word in the urban dictionary, one meaning for the word is "Commonly used to describe the embodiment of someone who retains a high level of sexual stamina and an insatiable libido, although keeping in tact a cool demeanor and reflective persona in which can easily charm either opposing, or same gender" and "Usually known as a guy with a MASSIVE penis". She said that the DAX contact was originally for an old female college friend and that DAX was her initials. She replaced her old friends contact information with this old boyfriends information. I have caught her in several small lies and my first instinct (and frankly what I truly think) is that she is lying in this case, but she swears that she did not know the meaning of the word. She is traditional Chinese and not someone that is particularly interested or knowledgeable in urban slang. So if she is not lying, I think this is quite a coincidence.