If there are still doubts about what was first the chicken or the egg, in the case of the Microsoft ETL (Extract-Transform-and-Load) tools, Azure Data Factory (ADF), and SQL Server Integration Services (SSIS) things are quite clear. SSIS was first.
You may say that it replaced Data Transformation Services (DTS) once the Microsoft SQL Server 2005 was released but in any case, ADF is a child of Azure and was generally available in 2015.
What is not that clear is when to use SSIS and when to use ADF? Glad you asked! Because Tim Mitchell has a detailed post about this. You can read it here: Comparing SSIS and Azure Data Factory.