Octopuses don’t actually have tentacles. They have eight limbs, but they're arms (for most species). Technically, when talking about cephalopods (octopuses, squids etc), scientists define tentacles as limbs with suckers at their end. Octopus arms have suckers down most of their length.
Mount Everest isn't technically the tallest mountain on Earth. Mauna Kea and Mauna Loa in Hawaii, the twin volcanoes, are taller than Mount Everest due to 4.2 km of their heights being submerged underwater. The twin volcanoes measure a staggering 10.2 km in total, compared to Everest’s paltry 4.6 km.
The fear of long words is called Hippopotomonstrosesquippedaliophobia. The 36-letter word was first used by the Roman poet Horace in the first century BCE to criticise those writers with an unreasonable penchant for long words.