This is the 86th most frequent Turkish word.
ettiği
"Ettiği" means "that he/she/it did" or "that he/she/it made" in English.
Here, 'ettiği' is embedded within the subordinate clause indicating a causative relationship with the main event described.
Bu olay, düşünce şeklimizde büyük değişikliklere neden olduğu için önemliydi.
This event was important because it caused significant changes in our way of thinking.
Here, 'ettiği' refers to the act or result of 'doing or making' that is being talked about (in participle form). It is connected to 'yaptı' (he did) and modifies the following relative clause.
O, yaptığıyla herkesi etkiledi.
He influenced everyone with what he did.
In this sentence, 'ettiği' signifies the action performed according to the main verb 'verdiği' (provided) and describes the information tied to the book.