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Lat. obvĭāre is another verb that seems to be formed following the same pattern as the previous ones, with the prefix ob‑ ‘in the way, against, toward’. This verb was several meanings and thus translations. These meanings can be divided into two groups: ‘to withstand, oppose, prevent, hinder, go against, to act counter to’ and, a very different one, ‘to (go out to) meet’.
It does not seem, however, that this Latin verb was derived from the verb viāre by addition of a prefix. Rather, it was derived from the adjective obvĭus (fem. obvĭa, neut. obvĭum), which meant ‘in the way’, ‘obvious’ and ‘meeting’, which is derived from the prefix ob‑ and the root vi‑ of the noun vĭa ‘way’. This Latin adjective is the source of the cognates Sp. obvio/a ~ Eng. obvious, borrowed in the 16th century in English and the 17th in Spanish. Note that English changed the ‑us inflectional ending of the Latin word with the ending ‑ous, which is typically the reflex of the Latin derivational suffix ‑ōs‑us/a, cf. Sp. ‑os-o/a.
The Latin adjective obvĭus seems to have been derived from an adverbial phrase consisting of preposition plus noun: ob viam ‘in the way, towards, against, etc.’. In other words, the adjective obvius came first, derived from the phrase, and was then turned into the verb obvĭāre by the changing of the inflectional endings without the addition of any derivational affixes.
Eng. obviate is a learned 16th century loan from the Latin verb obvĭāre’s passive participle obvĭātus. Actually, it seems that the post-classical Latin noun obvĭātĭōn‑, derived from this verb, was borrowed into English first, in the early 15th century, resulting in the noun obviation, which was used at different times with the two main senses that the verb had in Latin: (1) ‘the action of preventing or avoiding something by anticipatory measures; prevention’, a meaning that obviation still has today in English, and (2) ‘the action of meeting or encountering something; contact with or exposure to something’, a meaning that is today obsolete (OED).
The English verb obviate means ‘to anticipate and prevent (as a situation) or make unnecessary (as an action)’ (MWALD) and it is thus a synonym of the verb prevent, e.g. This new evidence obviates the need for any further enquiries and Disaster was obviated by the opening of the reserve parachute (OALD). English obviate translates into Spanish as hacer innecesario (lit. ‘to make unnecessary’), eludir (cf. Eng. elude), evitar (lit. ‘to avoid’), and even by the very rare cognate verb obviar, a transitive verb that means ‘to avoid, to shun, to remove obstacles or problems’ (Sp. ‘evitar, rehuir, apartar y quitar de en medio obstáculos o inconvenientes’, DLE).
Curiously, Spanish had a patrimonial verb uviar derived from Lat. obvĭāre, now obsolete, which meant ‘to come to, arrive’ (‘acudir, venir, llegar’, DRAE). This sense obviously came from one of the senses of the Latin verb obvĭāre that we saw earlier, namely ‘to come out to meet’.
Sp. extraviar ‘to mislay, lose’ would also seem to be formed from the same pattern that we have seen before: Latin preposition + vĭāre. There is a Latin preposition extra ‘outside of, without, beyond, etc.’, but there is no Latin verb *extravĭāre and no other Romance languages seem to have cognates of it. This Spanish verb appears to be a neologism, created in Spanish, first seen in a dictionary in the 18th century. It is primarily a fancy synonym for the sense ‘to mislay, lose’ of the verb perder, e.g. Extravié las llaves ‘I lost my keys’. (The first definition or sense of this verb in the DLE is ‘to lose something or to not know or forget where it is’.) As expected, the reflexive (pronominal) form of this verb, extraviarse, translates as ‘to get lost’, e.g. Me extravié ‘I got lost’, Se me extraviaron las llaves ‘I lost my keys’. There is at least one set expression formed with this verb, namely extraviar la mirada ‘to avoid looking at something or someone, to avert one’s eyes’. Curiously, this verb was much more common in the 19th and early 20th century than it is today and thus there is an archaic feeling to it, which is probably what makes it seem rather fancy or formal.
Note that though there is no Latin verb *extravĭāre, there is a phrase extra viam in Latin that means ‘outside the road’ and which could have influenced the creation of this neologism in the way that the phrase ob viam is the source of the Latin adjective obvius and, thus, of the verb obvĭāre (see above). There is no evidence for that, however. Do note that the phrase extra viam is used as a technical term in common law. It is used for instance in the phrase extra viam rights, which means
The right of a traveler upon the highway to travel over the abutting property where the highway is out of repair and impassable for practical purposes. 25 Am J1st High § 615. The right of one having an easement of way to depart from the regularly traveled way or path and pass over the abutting land of the servient owner where the latter has obstructed the private way or made it impassable. 25 Am J2d Ease § 70’ (Ballentine’s law dictionary).
Other minor (and less common) senses of the verb extraviar are ‘to mislead’ (a person), ‘to make someone get lost’, or ‘to lead astray’. The reflexive version of this verb, extraviarse, has the intransitive meaning, namely ‘to get lost’, ‘to get mislaid’, ‘to go missing’, as well as ‘to lose one’s way’ (syn. perderse). Other senses are ‘to go astray’ and ‘to be mistaken’.
The associated noun is extravío ‘loss’ and the associated adjective is derived from the past participle, namely extraviado/a ‘lost’. The primary meaning of the fancy and rare noun extravío is ‘the action or result of losing something or getting lost’, which is synonymous with the noun pérdida ‘loss’, e.g. Han denunciado el extravío de un paquete postal ‘They have reported the loss of a package’ (GDLEL). Another, less common sense of this noun is ‘bad or altered habits or behavior’, e.g. los extravíos de la sexualidad ‘sexual deviations’ (AEIV).
 The derivational suffix in question was ‑ōs‑, followed by the nominative inflexional endings (masculine) ‑us, (feminine) ‑a, and neuter ‑um. looked like ‑ōs‑us. English did this spelling change with many other Latin adjectives ending in ‑us that it borrowed.
 The noun obviation has acquired a new sense in modern American linguistics, one introduced by Leonard Bloomfield in 1927, namely ‘the marking of a subsidiary third person (in Algonquian and certain other languages); the expression of the obviative [case]. Cf. obviative n. and adj.’ (OED).