The California General Corporation Law authorizes the adoption of bylaws, but does not purport to define the term.  Cal. Corp. Code § 110.  The Nonprofit Corporation Law defines "Bylaws" not by description but by stating what they include.  Cal. Corp. Code § 5037 ("'Bylaws' includes amendments thereto and amended bylaws.").  In contrast, the Nonprofit Religious Corporation Law provides an actual definition:

“Bylaws,” as used in this part means the code or codes of rules used, adopted, or recognized for the regulation or management of the affairs of the corporation irrespective of the name or names by which such rules are designated.

Cal. Corp. Code §9150(a).  Thus, only in the case of a nonprofit religious corporation is it clear that bylaws do not need to be denominated as such to be bylaws.

Why It Takes A Village To Make A Bylaw

Oddly, we can thank the ninth-century Viking invaders of England for the term "bylaw".  The Vikings, including those from Denmark, invaded and ruled a large swath of England.  That region eventually began to be called the Danelaw.  The term "bylaw" is derived from the Old Norse words bi-lagu.  Bi refers to a place where people live such as a village and lagu means law.  See Just What Does Deem Mean?  If you look at a map of England, you can quickly find areas that were once under Viking control by looking at the town names.  English towns with names ending in -by, -wick, -howe, -thorpe, and –thwaite are generally found in the former Danelaw.  Note that -by ending found in town names such as Selby and Utterby is the same by found in the modern English word "bylaw".