Not sure. When i was younger i did had this occasionaly. Poor word articulation sucks in social situations.
Sometimes i would also say everything really fast to someone so i guess they really felt uncomfortable and did not hear a thing i said. I remember i had this alot when i was 16. Not only did i talk fast, it was also pretty emotionless.. like i was an android or something.
After watching TV series and anime for years, i sorta learned how to 'speak' in a calm and more artistic way with various tones. Now i appear almost human i think, coming straight out of a TV. Too bad i'm the one to know it is all 'fake'