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Kneel, like what you do when you stand up, as it were, on your knees during the Consecration, or, if you're disobedient to the local ordinary, what you do in your pew after receiving Communion.
OB (like in obtuse, or an angle greater than 90 degrees but less than 180) + stat (like in statistics, or what they say in the hospital to mean "hurry up"). BTW, has nothing to do with obstetrics.
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