The principal role of cementum in tooth anatomy is to serve as the medium through which the tooth is anchored to the surrounding alveolar bone. Cementum is a specialized calcified tissue covering the roots of the teeth. It provides a surface for the attachment of periodontal ligament fibers, specifically the Sharpey's fibers, which embed into the cementum and into the alveolar bone. This connection stabilizes the tooth within its socket, allowing it to withstand mechanical forces during chewing.

Key points to note:
- Cementum covers the root surface of the tooth.
- It acts as an attachment site for Sharpey's fibers.
- These fibers are part of the periodontal ligament, which connects the tooth to the alveolar bone.
- Cementum does not provide nourishment to the dental pulp; this function is related to the blood vessels within the pulp.
- It does not protect enamel from acidic dissolution; enamel is protected by saliva and other factors.
- Cementum is not involved in the formation of dentin; dentin is formed by odontoblasts during tooth development.

Therefore, the correct answer is:
Attachment of the tooth to the alveolar bone via Sharpey's fibers

Reference:
*Ten Cate's Oral Histology, 9th Edition, Chapter 7: The Periodontium and Tooth-supporting Structures*