"why" can be compared to an old Latin form qui, an ablative form, meaning how. Today "why" is used as a question word to ask the reason or purpose of something. This use might be explained from a formula such as "How does it come that ...". If you meet an old friend of yours, whom you never expected to meet in town, you can express your surprise by saying: Why, it's Jim! This why in the ...
The history told me nothing why an involuntary, extremely painful spasm, is named after a horse called Charley. Charley in the UK is often spelled Charlie, a diminutive of Charles, and it's also used to call a foolish or silly person. Who was Charley; was it the name of a horse?
The grass is wet because it rained last night. This seems the simplest and most elegant expression of the meaning. I am always suspicious of "reason (s)" and "why" being next to each other. There can be reasons for things but there is usually a better way of expressing "reasons why".
As to why someone would avoid the use of Daddy, other than family culture (my parents were always Mom and Dad; I have no idea why), well, yes, there could be some confusion, but I don't think the notion of censoring oneself from using Daddy is all that common, especially among parents. Is the primary usage of “Daddy” sexual now?
This Wikipedia article gives this explanation for the origin of the word gee-gee: The Chester Racecourse site was home to the famous and bloody Goteddsday football match. The game was very violent and, in 1533, banned by the city, to be replaced in 1539 by horse racing. The first recorded race was held on with the consent of the Mayor Henry Gee, whose name led to the use of ...