Betelgeuse is a red supergiant star hundreds of times of the diameter of the Sun. It expands and contracts over period of months and year, changing brightness noticeably in the process.

The 10th century Arabic astronomer al-Ṣūfī said in his "Book of the Fixed Stars" that this star was known both as "mankin al-jauzāʾ" (the shoulder of al-jauzā) and also "yad al-jauzā" (the hand of al-jauzā). The name "Betelgeuse" comes from the second of these alternatives.

al-jauzā was the name given by the Arabs to the large constellation that they saw in this area. The word al-jauzā apparently comes from the Arabic jwz meaning 'middle', so al-jauzā means something like 'the lady in the middle'. The reference to the 'middle may be to do with the fact that the constellation lies astride the celestial equator.

The Greeks did not give a name to either Betelgeuse or Rigel, surprisingly for such prominent stars, which is why we know them by their Arabic titles.
—Ian Ridpath (2018) "Star Tales"
Experts trace the name back to the Arabic yad al-jawza'. A transcription error, confusing the initial letters b and y (in Arabic, ba and ya) because of their similar shape, dates back to the 13th century when a star table by John of London named the star Bedalgeuze.
— Robert Lebling (2010) "Arabic in the Sky Saudi Aramco World

Supernova explosion

Betelgeuse, the closest red giant to Earth, has long been understood to move between brighter and dimmer in 400-day cycles. But from late 2019 to early 2020, it underwent what astrophysicists called "the great dimming", as a dust cloud obscured our view of the star. Now, it is glowing at 150% of its normal brightness, and is cycling between brighter and dimmer at 200 days intervals. Research concludes that it will be five to 10 years before Betelgeuse return to its normal 400-day cycles.

One of the coolest things about Betelgeuse is that we're watching the final stages of big star evolution play out almost in real time for us. Observing its behaviour gives important insights into the behaviour of red giants before supernova explosions. When it does eventually explode, it could -- over the course of a week- grow so bright that it will be visible during daylight and cast shadows at night. There are records from ancient Egypt of what appears to be a star exploding as a supernova. The Egyptians described the appearance of a "second sun" in the sky.

Betelgeuse is expected to explode some time in the next 10,000 to 100,000 years. While Betelgeuse is very unlikely to explode in our lifetimes, "we don't know", says Dr Sara Webb, an astrophysicist at Swinburne University of Technology in Australia, "theoretically it probably hasn’t, but theoretically it could have exploded and we wouldn’t know."
— Helen Sullivan (2023) "‘It’s new territory’: why is Betelgeuse glowing so brightly and behaving so strangely?" The Guardian