The story
From aldehyde + -anine, in reference to aldehyde, with the infix -an- for ease of pronunciation, when the German chemist Adolph Strecker first synthesized alanine in 1850 by mixing acetaldehyde (then just known as aldehyde) with ammonia, hydrogen cyanide, and hydrochloric acid.
Etymology from Wiktionary, CC BY-SA 4.0.