From Zelda Legends Wiki
For years, Zelda fans believed DethI to be spelled with a lower case "L" at the end. However, the Japanese name was found to be デスアイ, "DESU AI," which seems to be "Death Eye" written in katakana. This is when it became clear that it is actually an upper case "I" at the end. A lower case "L" and an upper case "I" look identical in many fonts, including the official NOA guide for LA. Everyone assumed it was an "L" at the end, seemingly because a pronunciation of "dethel" seems to come more naturally than "deth eye" to Western ears.