I learnt recently that the word quasar is a portmanteau from quasi-stellar. A portmanteau is a word made from bits of two other words, the canonical example being brunch (from breakfast and lunch). We have lots of them, and they tend to be a bit silly, like spork or celebrity nicknames like Jedward. Interestingly, Tanzania is a portmanteau, from Tanganyika and Zanzibar, the two countries that made up the new independent republic.
What struck me about quasar is that it's a noun (it's a very energetic and distant active galactic nucleus, according to Wikipedia), but it's formed from an adjective (quasi-stellar). Looking into it, it's quickly obvious that it's because quasi-stellar is only part of a longer noun phrase, quasi-stellar radio source. Presumably, bods at quasar research facilities referred to them first by their full name, then pretty quickly shortened it to quasi-stellar (the radio source part can be assumed, after all, when what you do is look at radio sources) and then that was the part that got blended.