All words in use today were made up at some point and then accepted through popular use. Merriam-Webster accepted this one into their dictionary some years ago.[1]

And Dictionary.com acknowledges it may have been published previously in 1884 by C.A. Ward as an example of a barbarous verb.[2][3]

[1] https://www.merriam-webster.com/dictionary/embiggen

[2] https://www.dictionary.com/browse/embiggen

[3] https://academic.oup.com/nq/article-abstract/s6-X/242/135/43...