The longest English word is nearly 190,000 letters. It’s the chemical name of Titin, the largest known protein that’s important for muscle contraction. There’s some debate over whether it’s actually a word but…can you imagine only getting paid 7 cents to write that?
The word penguin comes from two Welsh words for “head” (pen) and “white” (gwyn). When you think about it, this makes little sense since penguin’s heads are usually black and their bellies white…but we’ve always known that English makes little sense, haven’t we?
As of 2018, tl;dr is listed in Merriam-Webster as an acronym.