early 15c., obstinaunce, "non-compliance, self-willed persistence," from Medieval Latin obstinantia, from obstinatus "resolved, determined, resolute" (see obstinate). Earlier was obstinacioun "determination, resolution" (mid-14c.), from Old French.
obstacle
obstetric
obstetrician
obstetrics
obstinacy
obstinance
obstinate
obstipation
obstreperous
obstruct
obstruction