The word 'yerba' entered English as a direct borrowing from Spanish, specifically in the context of the South American beverage culture. Its ultimate origin is the Latin word 'herba', which broadly meant "grass, green crops, herbs". In Spanish, the initial 'h' of Latin 'herba' became silent, leading to the spelling 'yerba'. English adopted this Spanish form to refer specifically to the plant used for making mate, retaining its specialized meaning. This journey from a general Latin term for vegetation to a specific English term for a culturally significant plant illustrates a common path of semantic narrowing through borrowing.

The word 'yerba' is a direct loanword from Spanish, where it functions as a simplex noun. It is derived from the Latin 'herba', meaning "grass, herb, plant".