I remember having books of riddles and puzzles as a child, and a question from one of them remains with me to this day:
“When is a door not a door?”
The answer: “When it’s ajar.” (Get it? A jar, which isn’t a door.)
In a similar way, now that I’m etymologically grown up, I’d rather ask:
“When is a bridge not a bridge?”
And the answer, following the pattern of the earlier riddle, is:
“Abridge isn’t a bridge when it’s abridge.”
The bridge—even a short one—that stretches over a river has nothing to do with the verb abridge that means ‘to make shorter.’ English took that verb from Old French abregier, which developed from the Late Latin abbreviare that meant ‘to shorten’ and is also the source of English abbreviate and Spanish abreviar. Late Latin had crafted its verb from the Latin adjective brevis, the predecessor of Spanish breve and, via Old French, English brief.
And that, in brief, is the story of abridge but not of a bridge—except insofar as this acts as an etymological bridge to the other side of phonetic confusion.