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Etymology

Lisbon's name may have been derived from Proto-Celtic or Celtic Olisippo, Lissoppo, or a similar name which other visiting peoples like the ancient Phoenicians, Greeks and Romans adapted accordingly, such as the pre-Roman appellation for the Tagus River, Lisso or Lucio. Classical authors writing in Latin and Greek, including Strabo, Solinus, and Martianus Capella, referred to popular legends that the city of Lisbon was founded by the mythical hero Ulysses (Odysseus). Lisbon's name was written Ulyssippo in Latin by the geographer Pomponius Mela, a native of Hispania. It was later referred to as "Olisippo" by Pliny the Elder and by the Greeks as Olissipo (Ὀλισσιπών) or Olissipona (Ὀλισσιπόνα).

Another claim repeated in literature is that the name of Lisbon could be traced back to Phoenician times, referring to a supposed Phoenician term Alis-Ubbo, meaning "safe harbour" or "pleasant haven". Although modern archaeological excavations show a Phoenician presence at this location since 1200 BC, this folk etymology "is never attested in ancient classical literature".

Lisbon's name is commonly abbreviated as "LX" or "Lx", originating in an antiquated spelling of Lisbon as Lixbõa. While the old spelling has since been completely dropped from usage and goes against modern language standards, the abbreviation is still commonly used.