I constrain, adjure, obtest and strongly command you.
-- Sir Walter Scott, Guy Mannering
And whosoever she be, even with the form of words which to miserable wretches is granted most exaudible, I pray, and do with those prayers most heartily obtest, which are in the ears of the hearers of them most effectual, that she may never taste of such bitter miseries.
-- Giovanni Boccaccio, Amorous Fiametta
Obtest comes from the Latin roots ob-, a prefix meaning "toward", and the root test, meaning "witness."