jury

Jury comes from Middle English jure, borrowed from Anglo-Norman juree, itself from Medieval Latin iūrāta — a form built on Latin iūrō, meaning "to swear or take an oath." There's also a separate, less certain sense of jury (as in jury-rigged) recorded from the early 1600s, whose origin is uncertain — possibly from Old French ajurie via Latin adiūtō, or possibly from a Frankish word *garu meaning "ready, prepared," related to Old English ġearu.

The oath-swearing root points to a group bound by a shared vow — fitting for a body sworn to judge fairly. The other, unrelated jury (meaning improvised or makeshift) seems to carry a sense of being "ready" or "prepared," if the Frankish origin holds.

If the Frankish theory is right, this makeshift sense of jury shares a root with the English word gear, both tracing back to an old idea of being "ready, prepared."