why do we call aquisition Utterance Initiator？

The term "Utterance Initiator" is not commonly used to refer to acquisition. Acquisition generally refers to the process of acquiring or obtaining something, such as knowledge, skills, or resources. It is not typically referred to as "Utterance Initiator."

However, if you are referring to a specific context or field where "Utterance Initiator" is used to describe acquisition, please provide more information so that I can provide a more accurate response.