Whatever it may have become in later years, Alan Kay, who is often called "The Father of Object-oriented Programming", outlined the message-passing idea as the main concept he was driving at, originally.

He also says that he probably misnamed it.

Here's a discussion in which the man himself makes a (small) appearance: https://softwareengineering.stackexchange.com/questions/46592/so-what-did-alan-kay-really-mean-by-the-term-object-oriented