Hopefully if you're reading this you know how people say Yoshi - "Yo-she" (listen to the Yoshi Rap if you don't know). But if you listen carefully to all of Yoshi's voice-overs, you'll see what he says is different - it sounds more like "Yaw-she". You might just accept this, but have you ever wondered why?
The Japanese for Yoshi is spelled out in Katakana, but since not all visitors to the lair will have Japanese text support, here's a page from Nintendo's Japanese Site - the first word (up to but not including the one in the middle that looks like a pretzel) in the letters is "Yoshi". The backwards E is the Katakana for "Yo" - But it's a rather short sound. The small =) smiley is Tsu, but when made smaller it indicates a pause - in Romaji (Japanese written with our alphabet) this is indicated by repeating the next consonant. The angled =) is SHI (as in sushi) and the dash after it lengthens the previous vowel sound.
So a direct Romaji translation looks like Yosshii (you might have seen Yoshi misspelled as Yossy in some places, this is probably why). A combination of the shorter Yo and the pause immediately after it makes it sound like Yaw-she. So, while all of the voice-overs in English games get changed to Yoshi (since the way we know it is more predictable to English speakers), Yoshi's sounds and voice-overs stay the same, probably so they don't have to get re-recorded (as you may have noticed, they haven't changed his voice since they recorded the sounds for Yoshi's Story).~Darkmark