Gaelic pronunciation rules account for many variations that seem inexplicable to the non-Gael. One example will illustrate. You should know that Scottish names are not always pronounced the same way abroad or even from one part of Scotland to another as many visitors find out when they pronounce local place names. When using name the lists don't be afraid to try equivalent or near spellings of the name. Often when a name is written phonetically, the original name will appear.
Writing is, after all, only a poor representation of what people say.
English speakers are keenly aware of the lack of agreement between the spoken and written language. Until about 1800 people wrote English as they heard and spoke it. There was wide variation in spelling even among educated men. Shakespeare wrote his own name several different ways during his lifetime.