The term kshetra-patni translates to "mistress of the field" (kshetra meaning field or land, and patni meaning mistress or wife). It is an agricultural deity associated with fertility and the evolving concept of land possession in ancient India.

Atharvaveda is the correct answer. The term explicitly originates in the Atharvaveda, where hymns (such as AV 2.12.1) invoke the "mistress of the field" to bless agricultural endeavors.

Rigveda is incorrect. While the Rigveda frequently invokes the masculine counterpart, Kshetrapati ("Lord of the Field," an agricultural deity found in hymns like RV 4.57), the feminine term Kshetra-patni is a later development that is absent from the Rigvedic text.

Ashtadhyayi is incorrect. Authored by Panini (approx. 4th century BCE), it is a foundational treatise on Sanskrit grammar and linguistic rules, not the origin source for Vedic agricultural deities.

Arthashastra is incorrect. Authored by Kautilya (approx. 3rd century BCE), this text deals with statecraft, economy, and land administration. While it extensively discusses agriculture (using terms like sitadhyaksha for the superintendent of agriculture), it post-dates the Vedas by centuries and is not the origin of the term.

Therefore, Option B is the correct answer.