ob-prefix

Etymology: < classical Latin ob (also op in inscriptions) in the direction of, towards, against, in the way of, in front of, in view of, on account of (of uncertain origin). Prepositions in other languages may be compared, e.g. ancient Greek ἐπί epi- prefix, but it is difficult to identify cognates with confidence.Used as a preposition, Latin ob is followed by the accusative. In combination with verbs and their derivatives, the b of classical Latin ob is assimilated to certain consonants, becoming oc- before c- , of- before f- , op- before p- , and apparently o- before m- (in omittere ). In combination classical Latin ob has the following senses (all of which are reflected in English use: compare sense 1): (i) In the direction of, towards; facing, in front of; as classical Latin obvertere to turn towards, oboedīre to listen to (compare sense 1a). (ii) Against, in opposition, as occurrere to run against, oppōnere to place against; often merely implying the injurious or objectionable character of an action (compare sense 1b). (iii) Upon or over; down upon, down; as obdūcere to draw upon or over, obligāre to bind down, occidere to fall down (compare sense 1c). (iv) Completely; sometimes pleonastic, as obdūrāre to harden greatly, post-classical Latin obdulcare to sweeten (completely) (Vetus Latina); often with a colouring of (i) (compare sense 1d). Sense 2 reflects a scientific post-classical Latin use, not represented in classical Latin, where ob- was rarely combined with an adjective (the chief example being oblongus oblong adj., which could hardly be in sense the model for these words). Apparently the prefix here represents ob- in post-classical Latin obverse , adverb (see obversely adv.). This prefix forms compounds in English from the late 18th cent., in French from the early 19th cent. or earlier.